Thanks a lot for your extensive replies!

Unironically, Fire Sorcerer is one of the strongest classes in the entire game.
Quicken Spell Scorching Ray + Regular cast Scorching Ray upcasted to the highest level with Draconic Sorcerer's bonus CHR modifier (On every single projectile) absolutely deletes targets.
Sure, you lose out on the double damage from Wet, but instead you just deal raw damage without need of any set up. You just fling a billion projectiles each doing a bunch of damage at targets (Of course, you can still add more damage with set up... Amulet of Elemental Torment while stood in Fire (Or Lava) also adds damage to each individual projectile)
Thanks for the suggestion, I'm going to try this out! 
I am aware of the power of Scorching Ray, of course, but mainly on Warlocks with Hex, since they automatically upcast Scorching Ray.
To be fair, there's more to the game than raw damage output.
The reason I go by damage first is that healing is comparatively weak in BG3, as has been widely established. The best healing is therefore the damage you prevent from being dealt, by removing the damage source. In other words:
Offence is the best defence. Especially on Honour Mode, any enemy you take out before they take a turn can make or break your run. In Magic: The Gathering logic, "I don't have creature removal, but I do have player removal"; removing a player automatically means they skip their turns. So it's ultimately about action economy.
Of course, there are other ways of making opponents skip turns, from slipping on ice surfaces (then again, that's obviously a major part of ice sorcerer, aside from raw damage) to confusion, hold person, and disarming. The latter conditions however are ones that opponents can make saving throws against, allowing them to return from the incapacitating state. There is no returning from the incapacitating state "death", with a few noteworthy exceptions (the undead in the Mountain Pass, and Sovereign Glut, of course, being able to revive other enemies).
- Abjuration Wizards can be the best tanks in the game. As Arcane Ward can provide a ton of damage reduction making you take 0 damage from most attacks when set up properly (Warding Bond, Heavy Armour, Heavy Armour Mastery, all the magical equipment that gives you an Abjuration spell cast to let you stack up your Arcane Ward for free)
- Divination Wizards have their Portent Dice which can completely warp the game. Making deadly enemy attacks fail or enabling your party to use powerful abilities that are guaranteed to work. This feature can actually vastly outstrip the raw damage of a Sorcerer when used correctly (Such as landing Hold Person and then having your party get guaranteed critical hits on a target for at least 1 turn)
I am aware of the power of both of these; on the higher difficulties, I'm already making my wizard Abjuration, rather than Evocation. The problem I've found is that Arcane Ward is fairly weak on lower levels, because it's quickly depleted - and at least on my first attempt, Abjuration spells that are reactions, like Shield, didn't actually build up any Arcane Ward. I have no doubt it's going to come online later. But that's kind of the problem with a lot of powerful builds. An extreme example is Hunter, which gets its best abilities at Level 11. Fine for Minsc, who joins the party at Level 12, but not really a reason to play a Hunter Tav.
As for Divination, the strength and flexibility of the Portent Dice would make it annoying to me, as I would constantly have to dismiss the reaction whenever I
don't want to use a Portent Die, which is still going to be the majority of dice rolls.

To be fair, that just stems from your outlook on playing Bard.
Bard itself offers a number of playstyles in the class. From the Lore Bard being basically a Sorcerer (Just instead of Metamagic you get access to Magical Secrets allowing you to use powerful spells from Divine casters), Swords and Valor Bards can be played like Fighters or Rangers. Then there's a supportive playstyle focused around buffing allies (And/or debuffing enemies)
Lore Bard is one I still want to give a try eventually. There always seems to be one subclass per class that is just outclassed by the other two (the two Wild Magic subclasses for Sorcerer and Barbarian, College of Valor for Bard, Arcane Trickster for Rogue etc.). So I get why they're adding a new subclass for each class in Patch 8, since many classes only seem to have two out of three subclasses which are actually viable.
Not really. It mostly comes down to your outlook of "Damage > All" and the limitations you impose on yourself because other classes are found as default classes on companions (As well as lack of understanding on optimal builds)
Like, you dismiss Monk as a class, despite it being literally the strongest class in the game for damage (Something you value highly). Due to how you're building it, with a focus on Dexterity instead of dumping everything but Wisdom and Constitution while using Elixirs of Strength to boost Strength to 21/29 and using Tavern Brawler, Manifestation of Soul and Fast Hands to pump out absolutely absurd damage.
Here you've jumped to conclusions.
As I've stated in the opening post, I actually do have a run as a Monk Tav, and I'm doing precisely the elixir-Tavern-Brawler thing that everyone else does. That's what I meant by "getting into the meta".
The reason I stated Dex, Con, and Wis are so important for Monk was precisely because I know you can just dump Str for Monks. So I didn't mean Str were unimportant as a stat for Monks in general, quite the opposite - only that it's unimportant for investing any skill points into.

The problem I have with Open-Hand Monks is that they're pretty much a glass canon, similarly to Warlocks. Sure, I could do a bunch of things, but most of them are going to be strictly worse than just Flurry of Blows (plus, on later levels, Stunning / Ki-Resonation Strike + Ki-Resonation Blast). Just like with Warlocks, I could cast one of my Warlock spells, but I really need a strong reason not to just use my action on Eldritch Blast 95% of the time.
A Monk in the party as a support damage dealer, like hireling Sina'zith, is fun to me - a Monk Tav however has little to no skill points left for Charisma, and that was the reason I brought up Dex, Con, and Wis. Especially on Honour Mode, I would still like the option to talk myself out of as many dangerous encounters as possible. Monks are already MAD, and Charisma isn't one of the stats they normally need. Warlocks, in contrast, are largely SAD, being able to do pretty much everything with Charisma - but they're just as much of a glass canon, thanks to Eldritch Blast and the occasional Hunger of Hadar.
I could not agree more! Poison damage really feels like it gets shafted in BG3. Early on after getting the game, I decided to go all-in on a poison dragonborn draconic sorcerer. It was so bad XD Cloudkill is pretty decent, yeah, but with so many enemies outright immune to poison damage it really seems kind of not worth it.
My first time casting Cloudkill was on my very first run during the battle at Moonrise Towers - and it promptly earned me the "Enemy of Justice" debuff, because a Harper was stupid enough to run into it, and apparently that's my fault. Luckily, that debuff didn't stick around as I went into Act III, nor did it cause anyone to attack me when I returned to Last Light Inn after the Ketheric fight (I went there to test this, so that I wouldn't lose even more progress by first proceeding into Act III).
On my second run, I cast Hunger of Hadar instead, placing it a little further in the middle of the room, so that only enemies got stuck in there, none of the Harpers - and made sure to quickly cancel concentration on it as soon as the fight was over (in turn-based mode, as far as I recall).
At least I found a use for Circle of Death (necrotic) on my first run, in the courtyard battle during the finale. :P On my second run, I've only used Circle of Death to clear out the rats in the Elfsong Tavern. "Kill lots of small things" seems to be the primary application for it, as I had heard in the meantime that Circle of Death is supposed to be a spell for villains only, so that they can kill a lot of civilians and thus earn the heroes' hatred.
Fighter is another top tier class for damage output due to Elixirs of Strength, Tavern Brawler and thrown weapons (Pike of Returning, Lightning Jabber, Nyrulna) and associated equipment can push out obscene damage with their Improved Extra Attacks and Action Surge.
I usually do that with Karlach, making her a Berserker for Enraged Throw instead. I added three levels of Fighter (Eldritch Knight) recently, but found it adds little extra value, so I turned those levels into Rogue (Thief) levels for the extra bonus action instead. I don't actually want to use any bound weapons, even though Karlach has all the ones you mentioned in her inventory, as her main weapon is the Harmonium Halberd that raises her strength, combined with the Mighty Cloth. Throwing the Returning Pike would lower her strength as soon as it returns to her hand. So now I have the trade-off of always having to run around to pick up my Lightning Jabbers etc. ^^
Throw Barbarian is still somewhat of a glass canon to me, again thanks to the bustedness of Tavern Brawler. Much like my Monk, Karlach spends most combats doing the same things. Lae'zel as a Battle Master at least gets to vary her manoeuvres, depending on whether a given enemy can be disarmed, tripped, shoved, goaded, frightened etc.
Then of course there's other casters that while they don't output as much raw damage as a Sorcerer (Or Evo Wiz) can still provide bunches of power to a party;
- Druids have their Call Lightning which is a super powerful spell that is very spell slot efficient while being able to summon support with Conjure Elemental and Conjure Woodland Being providing more damage and control to a party. Spore Druids also can access the chest armour in Act 3 that lets them use spore buffs at will, enabling full uptime on Haste Spores that can give your entire party Haste (Without need of Concentration like a Sorc using Twin Spell Haste does to provide the effect to only 2 characters). Of course, Haste is less potent on Honour Mode but is still very good (And is outright OP on any other difficulty)
- Clerics have great support, synergies with Radiant Damage which when combined with Radiant Orb items can debuff enemies severely. Then there's also Tempest Domain which has hilarious power of control, namely things like using the Watersparkers (Plus the Sparkswall) to stand in pools of water, electrifying them and then in combination with their 6th level bonus making it so anything that touches the electrified water gets knocked back, creating impassable terrain for enemies (Or outright gluing them to a wall/corner constantly taking damage and being pushed back into the wall)
- Warlocks have potential for some very strong damage that doesn't rely on spell slots. Eldritch Blast with the Agonizing Blast invocation will add your CHR bonus to each projectile. Add on the Potent Robe from Act 2 and you're now dealing double your CHR bonus on each projectile. From there you can multiclass Sorc for Quickened Spell (Or Twin Spell) for more Eldritch Blasts per turn. Or Evo Wiz and get INT bonus on all damage types (Including Eldrich Blast's Force damage). Sprinkle on some Hex for more damage per projectile or you can use your Concentration and spell slots on control with things like Hunger of Hadar or Hold Person... Or even more damage with Wall of Fire (Which is super funny when you also have the Repelling Blast invocation and can toggle it on to knock enemies back into the flames if they leave them)
I'm already using those in my current playthrough, precisely because I'm playing an Ice Sorcerer Tav. 
Obviously, Druids and Clerics who can cast Create Water and Call Lightning synergise well with this. The Spark equipment set I gave to Wyll, and he kept it for the majority of my current run. The Potent Robe is worn by my Tav.
This synergy makes the build even more powerful - but also the entire team more one-note. Why should my Druids ever use any of their Wildshapes, if they can just keep casting Call Lightning? Sometimes, I turn Halsin into a Water Myrmidon, because the attacks synergise with the Wet condition.
Shadowheart (Tempest Cleric for Destructive Wrath) at least occasionally gets to do Spirit Guardians + Click Heels - i.e., a different damage type (Radiant) - but only when there are a bunch of small enemies to take out, like Cazador's bats. As long as there are sponges of enemies to take out - keep in mind Tactician Enhanced raises the HP to compensate for the higher party limit - making everything wet and then just spamming lightning and cold damage onto enemies to take out individual opponents before they get more than one turn is usually the most efficient strategy.
Wyll, as said before, is mainly just doing Eldritch Blast - I don't even need to do the whole Darkness setup - and Hunger of Hadar really only comes up occasionally for large enemy groups. That's usually when the Druids finally get to do something different, casting Spike Growth and Plant Growth. Wyll's spell slots in the end game are often best used by summoning an elemental - especially if I have to short-rest anyway, and Wyll still has one spell slot remaining, might as well summon an elemental. Again, though, I rarely see a reason to summon anything other than a Water Elemental, because of the cold attacks.
So as you can see, it's not just that Ice Sorcerer is one of the strongest builds - it's that the builds it synergises with are also some of the strongest builds for the other classes. 
I do want to try out what it looks like when I build my entire team around fire damage (Fire Sorcerer, Light Cleric etc.). But I assume that's quickly going to devolve into barrelmancy, at least when it comes to large enemy groups. Grease alone won't add as much damage as Water does for Cold or Lightning damage. The Scorching Ray thing is probably most comparable to the Call-Lightning or the Twinned Ray of Frost thing: Great for taking out individual enemies with large health pools, occasionally two enemies at once, but not large crowds.
Light Cleric is ironically more defensive than Tempest Cleric, thanks to Warding Flare. So whether I'd make Shadowheart a Light Cleric on Honour Mode is dependent on how scared of dying I am - picking Tempest Cleric for more damage is the greedy option. Much like Oath of Vengeance Paladin for even more damage vs. Oath of Ancients for healing.
Really it's mostly just Rangers and Rogues that kind of pale in comparison to other classes. Not that they're "Bad" just that they don't offer the same level of power as other classes if focused on (Rogue is often multiclassed in powerful builds because of Fast Hands providing extra bonus actions - Especially for classes that can make good use of them like Sorcerer Quickening 2 spells out to cast 3 leveled spells in one turn, Monk having their bonus unarmed attacks and most builds that use Great Weapon Master or Polearm Master feats or dual wielding for bonus action attacks)
I found Ranger the most disappointing class overall - the main one I hear people gushing about is Gloomstalker, but of course in combination with Assassin Rogue. Considering all the hoops you have to jump through to recruit Minsc, and how late in the game you get him, on my first run, where I didn't re-spec anyone aside from Shadowheart (into Light Cleric when the story called for it

), I was extremely underwhelmed by Minsc. Now he's a Berserker/Open-Hand Monk/Fighter without any Ranger levels, and I don't miss them at all. Lightning Arrow alone, despite being unique to Rangers, isn't worth taking all the other sub-optimal features. So Ranger is the class I'm most curious about when it comes to Patch 8, hoping the new class will finally make me actually want to play a Ranger, rather than playing one out of a sense of obligation, merely because Gloomstalker is OP.

@Strato: Out of curiosity, what's your pick for the best level 6 spell between Otto's Frozen Sphere, Chain Lightning, and upcasted Cone of Cold? I'm not going anywhere with this and I don't plan on responding to your answer specifically, I'm just genuinely interested in which you like better.
Chain Lightning, no questions asked.

I've always had a soft spot for Cone of Cold, but after having watched Cephalopocalypse's rankings of the spells, I agree that a lof of the Level IV and V spells have pretty underwhelming average damage when compared to Level III spells, and just upcasting those.
Otiluke's Freezing Sphere can only be learned by Wizards, much like Ice Wall, and it's not strong enough for me to shift from Sorcerer to full-on Wizard. Especially considering that you can buy plenty of scrolls for both Freezing Sphere and Ice Wall, and just cast those as a Sorcerer. Better yet, a single level of Wizard is enough for a Level-11 Sorcerer to learn these spells. I even saw a build yesterday where somebody managed to take two levels of Tempest Cleric on top of that, while still being able to cast Level-6 spells.