Blood is probably the best by far. Blood and prot pally are my fav tanks at this level for sure. I like frost, but survivability wise, i'v had better luck with unholy, I think unholy has better potential in bgs and such with clawing shadows range and the disease spread with solid gear as well. Frost doesn't seem bad don't get wrong, but i think you can be locked down way quicker if someone's smart, with unholy, at least you have a bit more presence, and the survivability of unholy is ahead a bit thanks to the pet shield now.