Concentration for Martials

[GeneralVryth]

I vibe with that. Obviously we're well into rewrites of large portions of the game, but I'd probably start by curtailing some of the random +1, +2 AC bonuses (looking at you warforged and forge cleric), reintroduce something like arcane spell failure, and nerfing the shield spell. I'd probably also try to tinker with something like reducing the headline AC of armor, and then let some classes apply their proficiency bonus to their AC once they reach a certain level. Finally, give armor DR but have it scale differently if the character gets their prof bonus to their armor. It would be a lot of fine tuning.

I also agree on the need to reduce the number of random AC bonuses. But I think you may have missed a key point about my suggestion. Armor wouldn't give AC at all. It would be purely a source of DR. Then put a basic AC bonus progression on different classes. The standard AC formula becomes 10 (or whatever) + Dex + Class Bonuses. With maybe some option to replace the Dex mod in some cases, or adding another stat if your not wearing armor. It creates the ability to approach mitigation by a combination of not getting hit and not taking as much damage. Something like a Monk can be actual evasion tank (tossing them an ability like Defensive Duelist or Shield with maybe a Ki cost would be elegant here), while Fighters use a combination of Armor and Skill (Class defense bonus) to both avoid getting hit and mitigating hits. Reaction options to reduce damage for a hit would also fit nicely in a Fighters wheel house. Barbarians of course lean more in to the mitigation front, likely getting some kind of natural armor (DR) plus rage bonuses.

On the caster front, part of the point of this is to put more of the defense bonuses and abilities into the classes themselves. This reduces that value of armor profs, and if you can combine that with making them a little harder to get (or requiring higher stats to use) casters getting access to those armor profs become a lot more balanced.

Maybe...I still think the problem is deeper than that. Consider HP bloat. Like monsters with 300+ hit points can't reasonably be taken down by weapon damage + modifier. So characters have to do A LOT more damage as they gain levels. And they do, to the point where they're one-shotting low level stuff. Conversely, a CR 2 that does ~7 damage a round after miss chance (this is being extremely generous to the CR 2 BTW), well that meant something when the characters had 45 hit points. But now they're level 14 and have 145 hit points. In a 3-4 round combat format, that's not meaningful damage. And yes, no one thinks CR 2's are supposed to be a threat by themselves, and not every combat has to be deadly++. But still like, what is the DM spending time on. Rolling for the 15% chance they inflict 2d6+3? C'mon.

Obviously in the DR system I am talking about there would need to be some re-balance of monster statblocks. Another nice thing about DR though, is you can reduce the HP bloat on both the PC and monster side. The trick of course is keeping baseline values in check. You don't want passive DR (from armor etc...) from going over 15, anymore than you want passive AC going over 25 by level 20 (And probably more 10 and 20 for level 10).

Side note, DR would mostly end low-level monsters as threats. With reduced AC lets say the hobgoblin veteran now has a 40% chance to hit. But they do 2d8+3 damage, or 5 - 19. A 3rd level fighter with DR 3? Sure, that hobgoblin is credible. But if the fighter has DR 10? Now the average damage roll of the hobgoblin does 2 damage. 32% of the time, the hobgoblin does no damage even on a hit.

That's why I talked about weapons and other attacks having a minimum damage that they can't be reduced below. It keeps lower level monsters relevant longer because of the risk of the death of a thousand paper cuts (also casters are less likely to be sporting DR so while a basic hobgoblin may more or less be forced into minimum damage against a Fighter or Barbarian, the Wizard or Sorc is still going to feel pain if they are hit). It also is another differentiation point for weapons. A longsword may be a d10 weapon but with a min damage of 1 or 2, while a warhammer could be d8 with a min of 3 or 4 (or maybe they would be 0+str mod and 3+str mod respectively).

As for how ablative armor works, my current version is a baseline AC of 8+PB, called Defense. So, anything that rolls below that is a full miss, no damage. Armor then provides an AC value that is added to that number. Take the current AC of an armor, subtract 10 and add the remainder to your Defense (+ Dex if the armor is Light or Medium (max Dex +2/+3 with MAM). That is your AC. Anything that hits between your Defense and your AC hits armor. Armor is rated with a number of Armor Hit Points (AHP) that absorb damage from a hit. If a hit deals more damage than the remaining AHP value, the remainder carries through to the PCs HP pool, and the armor is currently useless (proving neither DR (if applicable) nor AC - so the Defense is now 8+PB+Dex. Obviously, a hit that is higher than the AC ignores the AHP completely and goes straight to PC HPs (whether it also bypasses DR is another question - I rule it does).

The amount of AHP provided is more campaign specific than fixed; for players, they're always wanting more - but taking other forms of 'temporary HP, from THP to the arcane shield provided by Abjuration, I wouldn't recommend more than 10 AHP per AC provided. It shouldn't make it longer to take out a PC than normal.

Of course, spells with saving throws bypass armor as normal. Spells with attack rolls can hit and deal damage to armor. If DR applies or not, is again, a DM call. In a simplified version, I'm ok with DR working.

Repairing AHP can be as simple as an appropriate skill check (Leather working, smithing) over a short rest. Might repair 1 AHP per point of the roll; no minimum DC. Might repair a fixed amount per rest. Using something like Mending might work (despite the spell description not accounting for it). I'd recommend no more than 10 points per casting. Even completely rent armor should be repairable, though you might need to scrounge up additional material if you're not using magic.

For monsters that wear armor, I use a simple formula of 1/2 HP = AHP, and 1/2 HP = new HP value. The AC, I keep the same, and just have a range of 10 to AC hit armor. This does make monsters generally easier to kill (especially with saving throw spells), but I see that as a plus anyway.

While I kind of see the value in this from a verisimilitude perspective, I wonder if it's over-complicating things. It's adding a couple more logical checks per attack. Where as a more basic DR system is just adding a mod on the damage roll (with a min value if you use my above example). It's also adding another value to track. While I do think 5e made some things too simple, the general idea of simplifying things where possible, and streamlining things does have value.

I think on the 4e thing, if it fell closer to Star Wars Saga Edition than it did it would have groked better.
In the first set of things I had trouble groking was AC vs Reflex Defense. Saga Edition had a similar set up to defenses rather than saves but they cut AC with Reflex Defense applying to standard attacks.
Also classes having a much shorter list of abilities, and groupings of those abilities into archetypes so that you could get a sense of what your characters range was helped alot.

I agree with this completely. A 4e that would have been more like Saga would have been received a lot better. Saga just suffered hard from the skills being used to attack/defend with (while following a different progression), and also the lack of bounded accuracy is even more noticeable in the Star Wars universe where characters in the stories are routinely driven off by basic soldiers.