[@Luminosity]

Good questions first of all. You are correct on the combat system in that only attacks that hit will cause HP loss. However, I will be controlling NPC enemies so you only have to worry about your own character's actions. How a hit is determined depends upon the type of enemy, the weapons they are welding, the type of armor the player character is wearing, and things of that nature. Battle is meant to be a dangerous affair so expect to take some damage during encounters. 

I think I would consider that light armor. If heavy armor is full body plate, then light armor could definitely be armor on only certain areas of the body. No armor is just that--no armor whatsoever. 

Finally, I like the idea for a warrior-priest order of sorts. Keep in mind though that magic is still poisonous so the scale and frequency of use could have serious repercussions on the members of this order. Depending on how you create it though, it could work.