Yeah... needless to say, I'm getting my butt whooped by this guy in TVHM. I'm currently lv39, and he's 41 so it shouldn't be that much of an issue... The problem that I'm having aside from underleveled guns, which is why I'm here, is that the thrown Buzzaxe doesn't seem to be able to hit his critical spots. Both of the charges on his back won't take damage from it, but they don't get reflected. So while his back charges don't take any damage, his overall health is still being depleted.
Unfortunately, his chest can't take damage from the Buzzaxe either. I'm pretty much running out of ammo trying to kill this guy, and I don't think I'd be able to survive without RTB.