here are your options on the best tanks:
Paladins:
1. Have aegis stance which greater increases P. Def. (Majesty aswell)
2. They have self heals so you can stay alive longer.
Downside: Only good for group pvp.
Hell Knight:
1. Not as much p def as the paladin but they have their panther which makes up for it. (have Majesty)
2. Alittle better for solo pvp than a paladin.
Downside: If your panther dies you will die.
Titan:
1. Have great p atk (espescially with Guts, Frenzy, Rage, and Zealot).
2. Great in olympiad.
Downside: low P. def.
Shillen Knight:
1. Have hex. ;D
2. Best solo tank (for me anyways).
Downside: Ok P. Pef
Those are the tanks i would suggest..
but it really up to you