Armor on certain classes actually often lets them survive a lot longer, but depends on the type and whatnot. While it's not a guarantee as it's RNG as well, Paladins for example have around 45% absorb and 15% deflect. That means at least more than half of the fight they're absorbing/deflecting on average 35%-40% probably. Most of the attacks for survivability have nothing to do with passive armor though, only active.
It wouldn't help them though, cause a class that doesn't deal damage means it's just prolonged more than anything, though they need some modifications, the main purpose is being a wall rather than DPS. I kinda guarantee if you threw heavy armor on lets say cleric and toss em a shield, they'd take way more damage. When I was testing no armor to armor on saurians, it made their survivability a lot larger.
Monks right now have +2 ag on dodgei/+1 attack which gives them a pretty advantage. Obviously the MR comes in a factor with spell defense too. I kinda see they are the jack of all trades and need a little tweaking anyways too. I dunno where you are coming in that they don't have armor, they do. Not as high as others, but wha, 0-10 points of ac from most medium armors. Armor a that point makes little difference if your fighting someone of around the same armor value, since both your survivability are extended the same. They get their AC bonus is the reason why obviously.
A problem though with most classes and not seeing the 'difference' is because alot of them seem to end up at 80+ armor, so even though the necromancer, sorc, etc has cloth armor, you pretty much give them a heavy boost by SS and then armor types don't matter for the most case. I'm no saying certain classes don't need it. but we can probably should split armor more.
In terms of Barbarians having heavy instead of medium, it's another 10-15% of absorb chance. It wouldn't hugely affect their outcome, just make them slightly harder to kill.
Barbarians only have 1.25 AGI less dodge, not 0%, and it's not a % modifier either, it's literally removing -1.25 AGI. If they are dying, AGI is the slight issue but it's not the main. I think most people base this off word of mouth that they don't dodge worth crap, but I'm just laying down the facts here. Sure if you had a HO another -1.25 would hurt more than lets say, a LING, but it probably not the soul problem then on them.
Perhaps its just me, but it just seems "weird" that they should have heavier armor... i mean they are supposed to be crazy murderers without much finesse.. running around in rags, but hey, killing alot.
I mean, yee say this but then are against things like slayers in cloth armor. If we're gonna be 'lorey' then people who move in the shadows don't use armor, they want the most fitness/non clunky/no sound. So if we're going to start bringing in lore reasons now to me it's weird that slayers have medium armor.
But I try to avoid thinking that way too, we're playing a fantasy game after all. I've seen barbarian types with heavy armor, i've seen them with no armor. I've also seen battle priests who wear heavy gear like knights, etc. There's a bunch of options anyways and I don't think we should be tied to 'what looks right' otherwise half our classes have problems.
I dunno what is the deal of having more classes that round people, no offense. I think it makes the game really boring, you can't balance anything in team combat like that either.
Anyways, if we want armor values to matter more, we probably need to stop trying to make everyones armor the same in the end with AC increases per class, AC spell buffs, etc.