Yeah, the resist system is pretty broken late-game. Your guys become immune to, our outright get healed by, all elemental effects, which is an especially apparent problem with warriors since they get that huge bonus all resist talent.
It's not really a warrior problem, though. I had a mage late-game that was doing the same thing you describe your warrior doing, although I guess he needed a little bit better gear to pull it off, and his damage was lower - at least single-target.
