The problem you are describing, the metagaming and disruptive behavior, are due strictly to the player, not the character. Warmage, rogue, paladin, sorceror, whatever the guy was running is immaterial since the behavior is still the same. Disruptive metagaming is what I'd call an out-of-character problem, and you can't fix an out-of-character problem with in-game actions. You have to solve this face to face with the player, not with his character. merelycompetent sums it very well in his post, so I won't go over the same ground again, but suffice it to say if the player won't shape up he needs to leave.
I've been gaming for many years, and while the majority of gamers I've encountered have been decent folks, from time to time you run into a jerk who seems to gain all of their enjoyment from acting disruptive, and every time you're better off without them. Give him a chance to mend his ways, but if not then ask him to leave. Good luck!