Heavy Armour is OP.
Act 1 it completely sucks though, when it's just crappy 14 AC which is the same as medium armour like the Breastplate +1 or Githyanki Half Plate.
But once you get Adamantite Scale and some of the later heavy armours that get that +2 (Or +3 for the Hellplate) DR it becomes super strong.
Umm, Adamantine Scale Mail is medium armour lol. Just proving OP's point.
+2 DR from heavy armour, +3 DR from Heavy Armour Mastery feat and Warding Bond and you take literally 0 damage from most attacks. AC is low? Who cares, hit me for 0 damage all you want.
Taking 0 damage from "most attacks" doesn't matter. Who cares? Enemies that deal low enough damage that you can reduce it to 0 also have extremely low attack rolls.
Therefore, their chance of hitting you in the first place can be reduced close to 0 also. And not getting hit in the first place is objectively better than taking 0 damage when you do get hit, because attacks often come with additional effects that require a mental save, like bleeding, paralysis, etc.
AC being high is better than DR being high. Especially because these encounters where DR can reduce damage to 0 are not difficult encounters in the first place.
The point of armor is to survive encounters you otherwise wouldn't. If you would survive the encounter either way, then it's not really doing much for you. Any health it saves you is irrelevant since you can gain it all back with a short rest.
But there are encounters in this game, in honour mode, that aren't trivially easy. Where bosses do enough damage to one shot some characters. Or where a character gets paralyzed and takes a bunch of big hits in a row.
And damage reduction is not gonna save you in those cases, where a reduction of 5 damage is meaningless because attacks are dealing 20 damage at minimum in the first place.
AC is way way better in that case. Yuan-Ti Scale Mail will get a high dex character to 24 AC before even adding other effects, AND it adds +1 to initiative.
And that's on top of the insane bonus you get to initiative just by investing in dex, because this game uses a d4 for initiative rolls. Not to mention rangers can get a +3 bonus from their class, absolutely crazy in this game.
What advantage do heavy armour users get, in exchange for losing all this? Pretty minor special effects that you can easily get from other sources by the time you can actually obtain the armour in question.
The ultimate irony is that the best heavy armour doesn't even require heavy armour proficiency to wear.
That's how afraid of making player choices matter Larian is. They made the best heavy armour available to every character.
So if you really can't help yourself and you just love that helldusk armour fashion too much, well that's fine. You don't need to make any investment toward it whatsoever.
Also, I'll add that Heavy Armour Mastery is not a good feat. It might be worth taking once you've exhausted all the other good feats for a martial character, but that's never going to happen in BG3 or most official 5e adventures, because the level cap is 12.
A list of feats that are better for a martial character than Heavy Armour Mastery:
- Ability Improvement (2 ability points are better than 1 point + 3 non-magical DR)
- Alert (DR doesn't matter if the opponent doesn't get to take a turn in the first place)
- Athlete (never wasting a turn translates to fewer turns your opponents get to take)
- Great Weapon Master (self-explanatory, build-around)
- Sharpshooter (self-explanatory, build-around)
- Polearm Master (self-explanatory, build-around)
- Tavern Brawler (self-explanatory, build-around)
- War Caster (self-explanatory, build-around)
- Savage Attacker (self-explanatory, damage => kill your foes before they can take their turns)
- Sentinel (self-explanatory, build-around)
- Martial Adept (I would never take this in BG3, but I'd take it before taking Heavy Armour Mastery)
- Resilient (I wouldn't take this either, but proficiency and +1 to WIS saving throws is better defense than 3 non-magical DR, since the deadliest conditions have WIS saving throws)
Finally, Warding Bond generally isn't worth casting either. So many better things for a cleric to do with a level 2 spell slot.
And just to be clear, I do use heavy armour in this game. But not because it's good. It's objectively worse than light or medium armour.
Even on the strength builds I like to play, you usually want dexterity gloves for the initiative, so you're better off with Yuan-Ti Scale Mail.
But I just like the way heavy armour looks. It's the coolest looking armour, and it's not
THAT much worse than light or medium armour.
So it doesn't hurt too much to use heavy armour. That means it's a matter of personal preference, basically.
The point I'm trying to make is just that heavy armour should be objectively better than medium armour, but with a higher cost.
It shouldn't be a largely cosmetic decision that doesn't really affect how much damage you take.
You should be substantially squishier if you don't invest in heavy armour, taking damage more often and in higher numbers.
But instead, you're actually slightly squishier if you DO invest in heavy armour, which makes the investment worthless.
DND 5e sort of has the same issue, but you are kind of forced to use heavy armour if you're a martial character without much DEX, because you take an AC penalty for having a negative DEX modifier.
That works in 5e because you don't prioritize DEX on every character in 5e for the sake of initiative. This is ultimately caused by the d4 that BG3 uses for intiative rolls.
Because the die is so small, bonuses are disproportionately large. FIVE times larger than in tabletop. That's a big deal, because it's impossible for a character with a high initiative bonus to roll lower than a character with no initiative bonus.
In 5e, +5 to initiative is great, but your range is 6 to 25, versus 1 to 20. So it's still possible for you to roll a 6 while an opponent rolls a 20, or anything in between.
In BG3, +5 makes your range 6 to 9, versus 1 to 4. That means it's literally impossible for you to ever roll lower than an opponent with no bonus.
So you want DEX on every character that can spare it. That's why every character wants the dexterity gloves. If you don't have enough DEX, you'll literally ALWAYS go last in every encounter.
So because you're investing in DEX anyway, purely for the sake of initiative rolls, you aren't going to have an AC penalty for using light/medium armour in the first place if you're building your character correctly.
With no AC penalty for using light/medium armour, there's no reason to use heavy armour. That was the reason to use it in DND 5e, which you can see if you look at the
armour table.