My slapdash "scaling AC" rule

[qwertyu63]

I have made up a rule that quickly creates a scaling AC setup.

Instead of getting your Dex modifier to AC, you get your Reflex save modifier to AC. This includes your base save from class levels, your Dex modifier and any other bonuses to Reflex saves you have; however, resistance bonuses to Reflex saves don't apply to AC. Anything that would take away Dex to AC instead takes away Reflex to AC.

I think this rule would work better if good saves were just (level/2) instead of ([level/2]+2), but you work with the tools you are given.

[braveheart]

if you wanted to fix that problem you could rework the calculation to be 8+armor+reflex+(whatever crap your players pull)
I am assuming that you are using a D20 system however, this idea does throw off class balance slightly by punishing classes with "poor" reflex saves by dropping their AC

[Stiq]

I could picture Lightning Reflexes and the like abusing this, but if you were careful and maybe pruned out some of the existing armor class boosting feats, I could see it working.

Reflex save boosting magic items would be in high demand, though (esp. Cloak of Resistance.)

I like to handle AC and saving throws a bit more similarly to 4e (everybody gets +1/2 level with the only difference being whether you get a starting bonus or not) but to each their own.

[Extra Anchovies]

You may want to take a look at the Dodge/Parry system in the Conan RPG from Mongoose Publishing (it's OGL-based, but they changed a lot). Every class has a Dodge Defense and a Parry Defense progression, and the progressions are good (+15 by 20th level), average (+10 by 20th level), and poor (+7 by 20th level). When a character dodges (which can be done as a response to any attack), they add their class dodge bonus and their dexterity modifier to AC; when a character parries (which can only be done as a response to melee attacks), they add their class parry bonus and their strength modifier to AC. Shields add to parry bonus vs melee and to dodge bonus vs ranged. Granted, that system has armor as DR (full plate gives somewhere around DR 9/— but no AC bonus), but it's also a very low-magic game, so there aren't as many native ways to boost AC as there are in 3.5. It's fairly similar to, and slightly more complex than just using Reflex saves, but adding the ability to parry in there can make melee a little more interesting.

[ace rooster]

so the fighter, paladin, and barbarian are not good at dodging blows, but the rogue is? Reflex save seems to be about situational awareness, rather than combat awareness. Reflex save to initiative I would be behind, but applying it to AC makes combat characters worse at combat than avoidance classes. This strikes me as bad design.

[Just to Browse]

You need some serious compensation for attack rolls since AC scales and can be boosted with feats easier. You also need compensation for blasting spells since Reflex is more highly valued.

[nonsi]

Have you considered adding 1/2 BAB (level-progression derived only)?
This makes the more martially inclined classes grant better defenses and minimizes the need to juggle many rule changes for a single purpose of modeling honed defenses via experience.

[ranagrande]

You should out the Defense Bonus alternate rule in Unearthed Arcana. That's basically what it does.