In my experience, tanks have by far the worst attitudes in this game. I rarely see a healer say anything negative, and DPS may give each other advice on rotations. But tanks just straight up complain about everyone else doing their job, and remind you of how great they (think they) are at theirs.

I was running CT yesterday, and a tank joined halfway through the dungeon, and must have mentioned how his loot "better drop" in alliance chat about 10 times. NOBODY else said anything like this, of course.