Like you, I have pretty much all Plate classes in this damn game.
Frost DK's are really solid from what I have read in Arenas right now. you should have two silence/ interrupts, loads of AE, and be able to take a slap to the face. I "think" if you go this route, you should be in blood presence, for the healing and mitigation, but don't quote me on that.
Depending on how good of a warrior you are, then go that route, but I have no idea what Spec. For me, its always Prot, I can't help but Tank on either of my warriors
I've yet to really PVP on my pallie, my few times in zerg BG's don't really count, and I think I captured the flag once or twice in WSG, but yea.