Armor is a subject that is very bothersome for most people. There is a level of abstraction inherent in the functionality of armor beyond what most mechanics have, and while abstraction in of itself isn't bad, the result was something that didn't really work. AC is sort-of dodging, sort of blocking, but the one thing most people expect out of armor, softening a heavy blow simply isn't there. Add to that that at high levels scaling is such that AC is almost always lower than attack bonuses, and armor may as well not exist. Indeed, many characters who run around in plain old regular clothes are better at avoiding damage than heavy armor wearers. This is something that I think most people will agree isn't right.
A common solution to this problem is to introduce mechanics such as the popular armor as Damage Reduction option presented in Unearthed Arcana. This mechanic has well documented flaws, primarily that the value of armor varies wildy from encounter to encounter, and scales poorly. At level 1 armor makes a character nearly invulnerable to many enemies, while at level 20, their armor is almost as useless as it was in the normal system.
The modifications proposed here are intended to change the core system surrounding armor to make it more valuable across all levels, and to provide an advantage for characters wearing heavier armors.
Fixing the RNG
The first step to making armor more useful is to bring the RNG in line, so armor can be more useful in a wider variety of situations. To fix the RNG, the following changes are to be made:
Natural Armor and Armor no longer stack
-Natural armor acts in all ways like regular armor that is a part of your body, and has no weight or other penalties.
Shields now provide a deflection bonus to AC
-With this change, Shields now provide a potentially higher and cheaper way to gain a deflection bonus to AC, but the two cannot be stacked. This does weaken shields, but for the purposes of narrowing the RNG this really had to happen.
Base Attack Bonus is added to AC
-This is the biggest change, but all characters get a scaling bonus to armor class. This both helps high BAB classes, and provides much needed scaling to keep up with attack bonuses. A character using the same gear at level 20 is going to have a much better defense than at level 1.
Iterative Attacks cap at a -5 penalty
-That is to say that PCs now follow the same rules for attacking monsters have always followed. So a level 16 Fighter on a full attack has an attack sequence of 16/11/11/11. This is done to ensure the attacks remain on the RNG, with the raised AC later iteratives were even more likely to be useless.
Base Armor is 5, not 10
-This is a simple change that was needed to make it possible to balance the RNG without rewriting all of the armors. The basic reason is because attack rolls get their highest attribute, but armor gets the armor value plus an attribute, at a value that's always equal to roughly 8. This means until attack attributes hit 8, armor has an advantage right out of the gate.
These changes pretty much cover it for how to affect player characters. High ACs are now doable without spending half your gold on assorted bonuses from gear. A 20th level character is now most likely to have an AC of around 45+deflection mod. Attack bonuses at this level are usually around 35-40, so this seems like a good place to be.
One further change currently under consideration is the limitation of deflection bonuses. For example making it so shields can't be enchanted with +x modifiers (though could still get +x equivalent enchantments, waiving the normal +1 minimum requirement), and capping deflection bonuses at +2 across the board. Currently a character can get 50-52 AC with full BAB, capped armor, and a shield, this is nearly impossible to be hit by a medium BAB character, and at this time I'm not sure that's a good thing.
Sidebar: Converting Monsters
Providing a Secondary Benefit for Armor
Converting Monsters to this system is a bit harder. Unfortunately, a lot of monsters have BAB that far exceeds their expected level. Additionally, most of them were given a huge amount of natural armor to keep their ACs up to par. Unfortunately without rewriting the monster manuals there's nothing I can do about this. I can provide a simple conversion guideline, but ultimately converting monsters will involve a bit of guesswork or modified mechanics.
The guideline I would go with is this: Natural Armor = (8+1/4 CR) - Dex Mod - Size Mod. This gets you a natural armor level roughly in line with player's armor levels, with a higher value for big creatures, and a lower value for tiny creatures. This will be important in the next section.
You can stop at this point, and most people probably will want to. The other half of fixing this is modifying BAB values of monsters with high HD to bring their attacks and defenses in line. There are basically two ways this can be handled. The first is to leave them as they are. Provide a misc bonus to AC to bring their AC after the natural armor conversion to their current AC levels, and leave the rest of the stat block alone. This method is simple and to the point, but has potential for imbalanced stats with certain monsters that will be very hard to overcome.
If you wish to fix that, the second method is to adjust BAB to be based off CR instead of HD. So a Dragon would have a BAB equal to CR, an animal would have a BAB equal to 3/4 CR, and an undead would have a BAB equal to 1/2 CR.
For example, converting a Dire Tiger: it is CR 8 large creature with a +2 dexterity. Using our formula above, this gives us:
Natural Armor = (8+1/4[CR]) - Dex Mod - Size Mod
Natural Armor = (8+1/4) - 2 - (-1)
Natural Armor = 8 + 2 - 2 - (-1) = 10 - 2 + 1 = 8 + 1
So the Dire Tiger gets 9 natural armor. As it is a CR 8 animal (3/4 BAB), it gets a +6 BAB. Thus its total AC is 5+6(3/4 CR)+9(natural)+2(Dex)-1(Size) = 21, which should be comparable to a PC of its level. Its attack bonus is +14 with its primary attack, and +9 with its secondary.
For comparison, a Level 8 Fighter with +2 weapon and armor will have a 22 strength, 8 armor, +1 dex, and 8 BAB. Giving him a AC of 5+10(armor)+8(BAB)+1(dex)=24 AC, and +8(BAB)+6(str)+2(enhancement)= +16 to hit with his highest attack, +11 with his secondary. Meaning the tiger hits him on an 10 with his primary, on a 15 with secondaries, while the Fighter hits the Tiger on a 5 with his primary, and a 10 with his secondary.
Okay, so now that the RNG is more or less fixed so that armor actually matters against level appropriate enemies, that leaves the other half of what I discussed above. To make armor actually make you better at taking a hit that isn't avoided completely. For this, I introduce a new spin on an old mechanic:
Armor and Natural Armor provides temporary HP equal to its armor value, that refreshes at the start of each turn. This value is multiplied by the number of iterative attacks you have granted by base attack bonus, capped at x4 (so x1 at +0, x2 at +6, x3 at +11, x4 at +16).
Yep, it's that simple. Your armor gives you a refreshing pool of HP, so when you take a hit, you can shrug part or all of it off due to your armor. Eventually they will break through the armor, but this ability allows you to soften a big hit, or block a few little hits before taking real damage.
As an example, a first level Rogue with a Chain Shirt will have 4 temporary HP that refreshes each round. A 11th level Fighter with +3 Full Plate would have 33 hp that refreshes each round.
Monsters work the same way, getting their natural armor multiplied for every 5 points of BAB above 1, with a cap of x4. So the Dire Tiger example above with 9 natural armor and +6 BAB gets 18 temporary HP each round, while the 8th level Fighter gets 20 temporary HP each round.
Optional Rule: Armor Degradation
This was originally brought up as a possible balancing mechanic for the much higher temporary HP pools initially suggested. With the change in the current iteration, this is not needed for balance. That said, there is a niche for people who enjoy a grittier campaign. This optional rule is for people who enjoy such campaigns.
When using this option, any time an attack reduces your temporary HP from armor to 0, the armor degrades slightly. Its armor value is reduced by 1, until you are able to repair the armor. This reduces both the AC bonus and the temporary HP gained from the armor each round. The reduced bonus remains until you take the time to repair the armor. Repairing armor takes approximately 15 minutes per point, and requires 5 GP worth of materials for each point repaired.
Should an armor have its bonus reduced to 0, fixing it requires access to a forge, and takes approximately 4 hours, plus materials equivalent to half of what it takes to craft the armor.
Original post within the spoiler. If you're confused by responses on the first page or so, it's because the responses were to this, and not the above post. It's the same basic concept, but implementation has changed a lot.
So I had a random thought on armor, and while there are a couple topics I could post it in, it is radically different enough I didn't want to put it in one of those. So here I am with a new thread on armor.
But here's the thought: What if Armor provided a pool of refreshing temporary HP, as opposed to making it harder to hit at all, or acting as damage reduction?
Since HP/temp HP is already an abstraction, I was thinking have it scale with level. Say the current armor bonus times half level (round up). So a level 1 character in leather gets 2 temp HP per round, while one with Splint Mail (the heaviest you can probably afford at level 1) gets 6 temp hp per round. At level 20, this is 70 hp per round vs 130 hp per round. (alternatively you could drop armor enhancement bonuses, and make it times level, giving you 40 hp from leather, 80 from a chain shirt, or 160 from full plate).
If you wanted a little more complexity/realism you could even say something like every time the armor's temp hp is reduced to 0, the armor's bonus is reduced by 1/2 level (or by level in the second scenario), until the armor is repaired (ideally repairs would be something that could be done in a few minutes of downtime). So if leather armor gets broken through twice, it's pretty much useless. On the other hand Plate is still at least somewhat useful until it's been broken through 8 times.
The downside of armor would be that max dex still applies, so you choose between more durability, or the ability to dodge more attacks with a high dexterity. This would be something ideally to go hand in hand with something to fix the RNG (a la add BAB to AC and iterative penalties cap at -5), so that the AC bonus from dexterity would matter more across all levels. This way you have a real choice, get hit rarely, but when you do get hit, it hurts. Or get hit frequently, but shrug a large portion of the damage off.
Anyway, what do you guys think? I personally think it's a good solution to the normal problems inherent in armor as DR, while accomplishing a similar feel. It's pretty rough at the moment, but I think it does have potential.