S Tier:
Light Cleric Drow or High Elf
Open Palm Monk Wood Elf (Gloves of Soul catching, Boots of Uninhibited Kushigo, The Graceful Cloth)
Githyanki Evocation Wizard
Dwarven* Berserker Barbarian dual wielding Tavern Brawler with the Dwarven Thrower and Nyrulna (they both return)
*or you can just use the mask of many faces to look like a Dwarf and the extra weapon damage will proc.
Honestly - even the most challenging fights won't last more than 2 rounds with this group so there is no need for anything but haste potions.
If you need a character dedicated to healing then your fights are lasting too long or you have Karmic dice on.
Not to disagree at all, I'm just wondering some things regarding the comp you are proposing :
- What is the purpose of the light cleric here ? You are saying that you don't need a dedicated healer with a good comp, point I totally agree with (My actual team comp right now is REALLY on the OP side so I VERY rarelyhave to heal). So what is a point to bring a light cleric ? Wouldn't be more logical to take a class that can do some side healing just in case while being a respectable damage dealer / buffer ? I'm thinking of another cleric subclass or maybe a druid ?
- Why are you specifically choosing a Githyanki for the evo wizard ?
Again, I'm not arguing against anything, I don't have enough knowledge to be in these kind of theory crafting about classes and comps... Rather I'm trying to learn more

As GloriousZote pointed out Githyanki have Medium Armor but they also get:
1) Innate Spells - jump, misty step, and mage hand.
2) They also get Greatsword and Longsword proficiency, so at lower levels as an Evo wizard you can be a frontline Wizard with a Hill Giant Strength potion, either thudnerin' them waves or slapping them faces.
3) They don't have the movement speed penalty that Shield Dwarves have
4) They are incredibly attractive as a race and I won't hear otherwise. Claiming they "don't have noses" and they "look like frogs" is just rude.
So you can easily hit 19 AC with good gear at lower levels and be incredibly useful at every level.
The key to a truly great build is that it pays dividends at level 1 and doesn't have to wait for some high end gear in Act 3 to work decently. I actually hate playing with players that think like that because 1) they assume the game will make it that far and 2) they just take up space suckking until they get their item that makes the build they have work.
Light Cleric is an incredible Utility class that can dish out massive damage and is extremely tanky.
1) Warding Flare /Impose Disadvantage on an enemy attacker 1/per turn uses Reaction.
2) Radiance of the Dawn - 2d10 + Wis mod - HUGE AOE that only hits hostiles - Channel Divinity
3) Fireball and Destructive Wave
Plus they bring all the usual utility that Clerics have - the only downside is they don't get any special weapon proficiencies or armor, but they are perfect for the Blood of Lathander which kicks so much ass in the shadow cursed lands. They also get Daylight as an Always prepared spell which is really nice. Daylight, as I am sure you know, blinds undead and shadow creatures, same as the mace.
Finally, and this is a big one, Drow and or High Elves get Perception as a racial + Wisdom is the key attribute in perception. Combine that with items that give advantage on perception checks and you have what is basically a "Perceptor" character. They always see stuff.
Jahiera makes a better Rogue/Monk than Astarion or a Better Cleric than Shadowheart because she starts with Perception.