Idea from D&D 4th on AC

[Rogier]

Hey everyone,

I was watching some video's and someone told about this idea in 4th edition.
It seems that in 4th edition you get a your level/2 as a AC bonus.
To reflect your experience in combat and to avoid damage.

I thought this might be a good idea!
I was thinking to add this to my game.
But then I wanted it to be level/2 -1. So you start to get a bonus once your level 3.

What are you thought on this?

[Quantum Steve]

Would creatures with racial HD get an AC bonus of 1/2 their HD?

[Rogier]

I don't know... could do that.

[John Kretzer]

One of the things with 4th ed...and I think Star Wars D20 had a similiar mechanic of gaining AC bonus based on class level...is that they are not other ways to gain AC really except though level. In the rules as is there is already something like this...The Monk.

I am not saying do not do this. Just be aware that ACs might get to really high levels in your game if you do this and don't curtail the other ways to gain AC.

Though personaly I would vary the way each class gain this AC bonus based on BAB progression...if you want to reflect combat train and experience

For a example:
Full BAB would progress at +1AC/ 2 levels
3/4 BAB would progress at +1AC/ 3 levels
1/2 BAB would progress at +1AC/ 4 levels

[Bob_Loblaw]

In 4E you also get a bonus to attack equal to your level/2. This balances out with level appropriate opponents. Against weaker opponents, they have a harder time hitting you and tougher opponents have an easier time. If you don't account for this, you will find that you are dealing with ACs that are way too high for anyone to hit.

Keep in mind that CR =/= HD. Often a creature has more hit dice than an NPC of equal CR. An adult white dragon is CR 10 but has 13 hit dice. The tarrasque, (AC already 40), would gain +15 more to its AC.

Also, would this be a dodge bonus? An untyped bonus? Natural armor? Would it apply to Flat Footed AC? What about Touch AC? How would this affect CMD?

I don't think its really necessary in Pathfinder. If you really want to do something like this, consider using this from 3.5.

[Staffan Johansson]

Rogier wrote:

Hey everyone,

I was watching some video's and someone told about this idea in 4th edition.
It seems that in 4th edition you get a your level/2 as a AC bonus.
To reflect your experience in combat and to avoid damage.

I thought this might be a good idea!
I was thinking to add this to my game.
But then I wanted it to be level/2 -1. So you start to get a bonus once your level 3.

What are you thought on this?

In 3e/Pathfinder, there are many ways to increase your AC on a permanent basis: magic armor, magic shields, amulets of natural armor, and rings of protection. You can also boost your Dex, although that won't help much if you're wearing heavy armor, and some items might give a point or two of Luck or Sacred bonus.

But in 4e, there are far fewer ways of increasing your AC, pretty much just magic armor (plus temporary boosts from various powers). A 4e ring of protection gives you a +1 item bonus to saving throws (which in 4e are not the same as saves in 3e/PF), and lets you boost a defense by 2 against one attack per day (retroactively) - it does not give you a permanent AC bonus. Essentially, a 4e character has four sources of increasing AC at higher levels: the level bonus, armor enhancement bonus, masterwork armor, and (if wearing light armor) increasing Dex or Int.

3e is (sort of) balanced around most classes not having an AC automatically increasing at higher levels, but rather needing magic items to get there. 4e is the opposite. Adding a level-based bonus to AC would probably work well for a low-magic campaign though, when a 10th level character can't expect to have a +2 kit of AC improvement.

[Lexarius]

In 4E, most of the derived scores are based on the Level/2 thing.

Instead of BAB, all classes get Level/2 + ability mod + proficiency bonus.
AC gets 10 + Level/2 + ability mod + armor bonus
Fort, Reflex, and Will are 10 + Level/2 + ability mod + class bonus
Skills are Level/2 + ability mod + proficiency bonus

Basically, everything scales with level at about the same rate, plus whatever static bonuses the character can get.

Equipment, feats, and more importantly monsters are all designed with this progression in mind. Whether or not they were designed *well* is another question, but Pathfinder definitely wasn't designed with this in mind. It probably wouldn't play well with it.

The 3.5 Defense Bonus variant mentioned above would probably be easier to work in.

Something from 4E that would probably be easier to work in is the "inherent bonuses" variant used in Dark Sun. Basically, the idea is that characters gain the enhancement bonuses they would normally get from magic armor, weapons, and amulets as they level up. The rate at which they get these is such that they're never behind the bonus curve, but they're never really ahead either, so finding a higher-level magic weapon would still be useful. Additionally, lower-level weapons with special properties continue to be useful without having to upgrade them all the time. (4E does not have ability score boosting items, but one could imagine providing similar bonuses to ability scores based on class to reduce the need to provide up-to-date belts and such).

[Asgetrion]

I think Lexarius and Bob are right... if you're going to go through with it, ditch BAB and add a similar bonus to everyone's attack rolls, too. Also, make sure that you either use less bonus types (spell bonus, magic item bonus, feat bonus) and get rid of all "buffs" that give untyped bonuses to AC or attacks. And definitely don't hand out magical items that would grant bonuses that stack (hence my suggestion of merging bonus types -- at least natural armor and deflection -- under "magic item bonus"). I don't think it will work as elegantly as it does in 4E, however, and it will require a lot of work on your part to balance this system.

[Krome]

check out Unearthed Arcana from 3.5 or d20srd.com for Defense Bonus.

I think this would work fine for you.

[Mon]

Something that we've tried with good results is using a level / 2 bonus to everyone's AC but removing deflection bonuses and enhancements to natural armour. This handily removes 2 of the "big six" items (if that's your bag) but there are a few gotchas (Barkskin and Nymphs both need a bit of rewording, for example).

It doesn't apply to racial hit dice unless the creature also has class levels, so it comes into play for classed boss monsters and monster PCs but not for everything in the Bestiary. The good folks at Paizo usually pile on natrual armour or something to get standard monster AC up to where it should be for "normals", anyway.

Just a thought.