D&D 5E Why no Proficiency bonus to AC?

[Xeviat]

Yes, if we were to put proficiency bonus on Armor Class, we'd have to use different numbers for armor AC values. But hear me out.

Monster save DCs are related to their CR. Monster Attack bonus is related to their CR.

Player Save bonuses (proficient saves, though I partially disagree with this) go up as they gain levels; player AC is largely static as they gain levels. Aside from the Monk and some Barbarians, light armor wearers will probably cap off their AC growth at level 8 (if they started with a 16 Dex, they can move to 18 and 20 at 4th and 8th levels). Heavy armor wearers cap off their AC once they can afford plate. Medium armor wearers cap off a little earlier (or when they spend a feat on Medium Armor Mastery, if they have the Dex for it).

But that's it. Monster Attack continues to grow while player AC remains the same. Is this because the game wants HP to be the defense against weapons after a certain point? As you gain levels, you're going to take more hits.

Yes, there are magic items that can shore this up, if your DM uses them. But there are also magic items to boost attack, save dcs, and saves. Magic armor doesn't take up attunement slots, but neither does a +1-+3 weapon.

I'm just curious about this dichotomy.

 

[dave2008]

That's a good question. Try adding it in your game and let us know how it goes. I like the idea adding your prof. bonus to your AC actually, but it would definitely change the BA of the game I would think.

 

[Horwath]

Your HP goes up a lot.

If both your AC and HP would grow fast then all low CR creatures would become irrelevant.

Low attack scaling and almost no AC scaling keeps them viable throughout the characters carrier.

Now a lvl12 fighter still must be afraid of a band of dozen orcs.

Or it keeps city guards always a danger for PCs if they decide to go beserk on town population.

keeping AC in low 20s at higher levels is great IMO.

 

[Mouseferatu]

Yep. It's part of the whole "bounded accuracy" package. They very specifically didn't want AC to scale with attack bonuses, so that lower-level characters can still hit high CR creatures, and low-CR creatures can still pose some threat to high-level characters. They want HP, not AC, to serve as the buffer at that point.

 

[abirdcall]

If ACs go up then what is actually happening is that neither attack bonuses or ACs will increase relative to each other. It is a treadmill.

All that accomplishes is being practically unable to be hit by weaker creatures. This is what we got in 3.x where you where impervious to ordinary people/creatures after a few levels.

Monster ACs don't go very high either.

 

[TheLoneRanger1979]

If ACs go up then what is actually happening is that neither attack bonuses or ACs will increase relative to each other. It is a treadmill.

All that accomplishes is being practically unable to be hit by weaker creatures. This is what we got in 3.x where you where impervious to ordinary people/creatures after a few levels.

Monster ACs don't go very high either.

Yep. It's part of the whole "bounded accuracy" package. They very specifically didn't want AC to scale with attack bonuses, so that lower-level characters can still hit high CR creatures, and low-CR creatures can still pose some threat to high-level characters. They want HP, not AC, to serve as the buffer at that point.

These two basically..... Add proficiency bonus to AC and the entire BA system falls apart. Then we back on power creeping feedback loop of i get stronger they get stronger..... I'm pretty sure i don't want that in my games.

 

[BoldItalic]

I won't add to the BA comments, apart from just agreeing with them, but will add this:

Why would my armour suddenly get tougher just because I've gone up a few levels? It's the same armour. It hasn't improved with age, like a bottle of wine. If anything, it's more battered and damaged through wear and tear and stopping all those attacks I've risked getting enough XP get the levels to get the Proficiency Bonus. Okay, we don't do armour damage in 5e.

You can buy better armour (up to a point, anyway). Your AC one of the few things in the game you can get better at by spending money. You can't buy hit points from a hit point merchant, you have to earn them by earning levels, but you don't have to earn your AC. It's not a suitable reward for strenuous and meritorious adventuring, if anyone can just buy it.

Armour is just armour.

 

[Horwath]

I won't add to the BA comments, apart from just agreeing with them, but will add this:

Why would my armour suddenly get tougher just because I've gone up a few levels? It's the same armour. It hasn't improved with age, like a bottle of wine. If anything, it's more battered and damaged through wear and tear and stopping all those attacks I've risked getting enough XP get the levels to get the Proficiency Bonus. Okay, we don't do armour damage in 5e.

You can buy better armour (up to a point, anyway). Your AC one of the few things in the game you can get better at by spending money. You can't buy hit points from a hit point merchant, you have to earn them by earning levels, but you don't have to earn your AC. It's not a suitable reward for strenuous and meritorious adventuring, if anyone can just buy it.

Armour is just armour.

I think that the OP is referring to "dodge" part of AC. As if you get more adept at dodging blows. Not as passively upgrading your equipment.


But, IMO that is abstractly described via higher HP pool and sometimes directly via raising dexterity.

 

[nomotog]

I thought about trying it. Not as a core thing that everyone gets, but as an alternative to armor. It kind of caps out under full plate, but it's also a lot more progressive. I think it could work.

 

[TheLoneRanger1979]

I thought about trying it. Not as a core thing that everyone gets, but as an alternative to armor. It kind of caps out under full plate, but it's also a lot more progressive. I think it could work.

If not cumulative with armor, it might actually work....