Ewww, no, NEVER use PvP gear to tank in! Exceptions are the spell damage weapons and 'maybe' a shield, but as for the rest of it, never.
As for avoidance on your weapon: ice is right. You don't need it on your weapon, and currently there is really only 1 weapon in game at level 70 that is itemized with that mindset: Crystalforged Sword. It would be nice to have a better weapon itemized for us Tankadins, but after that sword, you just want a high stam/spell damage weapon, and leave all avoidance stats to the rest of your gear.