Swords 'n' Spurs: A Wild West setting with tweaked mechanics

[Hodge Podge]

Hey everybody!

My group has started a new Pathfinder campaign with a few little twists. It's the first game I've ever been in charge of, so if you all don't mind, I'd like to use you guys as a sounding board for my ideas.

Probably the biggest change is the near-total lack of magic in the game. There are still many fantastical creatures, and some mystical stuff such as dream-walking, undead, elemental spirits, and potion-like potables. Needless to say, several base classes are no longer viable. Classes like the gunslinger are now at the forefront.

For this first post, I'm just going to explain the basic changes in battle mechanics that we've made.

AC and DR

Spoiler:

We have decided to use an "armor as damage reduction" mechanic for this setting. Basically:
- Flat-footed AC is now equal to 10 + size mod.
- What was touch AC is now "Dodge", and it is equal to 10 + Dex + dodge + shield + size (there is no longer a deflection bonus). All melee and ranged attacks now target Dodge.
- Damage Reduction (DR) is now equal to armor + natural + enhancement + other DR bonuses.

"Taking Aim"

Spoiler:

To balance this huge increase in DR, armor with a bonus of more than 4 is hard to come by. In addition, combatants may add a penalty to their attack roll in order to overcome DR. This penalty must be applied before the roll is made. We explain this as the combatant "taking aim" at the weak points in the opponent's defenses:

A goblin with a Dodge 14 and DR 3 is attacked by a rogue with +5 attack. The rogue can just make a direct attack. If he rolls a 9 or higher he hits. If the attack does, say, 1d4+2 damage, the rogue would have to roll at least a 2 to do any damage at all.

If the rogue "takes aim", he may choose to subtract any number from his attack roll, thereby reducing the goblin's DR by the same amount (to a maximum of the goblin's DR, subtracting more than the DR does not do extra damage). This adds a fun level of uncertainty, as the players are seldom aware of their opponent's DR value:

The rogue attacks again, this time subtracting 4 from his roll to bypass the goblin's DR. This means he must now roll at least a 13 to hit the goblin. If he hits, the goblin's DR is reduced to 0 (it cannot become negative), and the attack will do full damage.

We've had 7 sessions so far, and the system is working fantastically for us. The players are taking maximum HP per level, and I've beefed up the enemies' HP a bit as well to account for the higher hit rates. Combat is very deadly and satisfying so far, and the players have come quite close to dying several times (One actually did. I pit them against a Spirit Naga when they were all still second level. It was awesome. They're lucky it couldn't cast spells.)

Also, sneak attack is ridiculous now.

Anyway, please provide me with feedback! If you think there's a way I could improve on this sort of system, I'd be more than glad to hear it.