For world quests, I can't say enough good things about 5x Prot Paladins. Mine are at about 845ish iLevel, and the only thing I can't do are world bosses and dungeons with the latter largely being that I dislike a lot of the dungeon mechanics for post-WotLK content.

I've been leveling blood DKs and they seem pretty good up through ~105ish.

My Demon Hunter tank group were also very good up through ~102.

None of them kill quickly on harder elites but they're very forgiving of mistakes.