Tank specs take extra damage in pvp, so they are rather lackluster in the early brackets (19, 29, 39, etc). I think they become more interesting at 59+, but I honestly don't know. For lower brackets, healers tend to be rather strong and hard to kill. A good disc priest or resto shaman is rather annoying.
You may want to look at a 110/111, where havoc DHs are the FotM. Some of that is more PvE oriented though.
The tankiest classes right now are healers. They do considerable damage, and bring survivability cooldowns. Very few players can 1v1 a healer, and god forbid you play one in a twinkless battleground, you'll tank 4-5 levelers at a time.