The problem of Reflex and AC being unrelated actually existed in 3E, too, but I think it was more noticeable in d20 Modern, where people are throwing grenades and automatic weapon fire, both attack types against armor should protect.
Moniker said:
Good point! Why not eliminate AC and make armor as DR at armor+1/2 level?
The designers unfortunately didn't want to abandon all of the sacred cows. Personally, I like the idea of armor as DR and adding to Fortitude. We houseruled it whenever we made our hybridized version of D&D from the Star Wars Saga ruleset.
They discussed this online a few months ago.
They tried it, but it proved to hard to balance.
And I've seen a few non-d20 games with armor as DR, and they are always unsatisfying from my gamist perspective.
Here are some points where you can get into trouble:
- Care about lightly armored archetypes? They suck against weapon damage.
- Care about mundane characters? They suck against spell casters that ignore your armor.
- Care about lightly armed archetypes? They suck against heavy armor
- Don't like usefulness/effectiveness of classes changing widely depending on monsters and NPCs employed? (Remember Rogue vs Undead compared to Rogue vs Humanoid? Think about Heavily Armored Warrior vs Spellcasting monsters to Heavily Amored Warrior vs weapon wielding monsters)
- Monsters with high damage output per hit are more effective then monsters with mutliple attacks, but lower damage output. (A problem I noticed in Iron Heroes)
It might be possible to balance this stuff, but it might also be just not worth your time.
Aside from that, comparing roll vs DC is always easier then subtracting numbers from rolls.
But I suppose there will be people trying to houserule Armor = DR, and maybe someone of them has a clever tweak.