Tanks.
I have resurrected a healer to run through dungeons for the DMF quest items (
Imbued Crystal is proving frustratingly elusive) and I keep finding tanks who are either arrogant, stupid or a combination of the two. I'm sure it's no one on here, but felt the urge to whine anyway.
Monk tanks seem to be the worst.
If you want me to heal you, don't LOS me. If you want to pull the whole fucking dungeon, make sure you can hold aggro (and maybe give the rest of the group a heads up that you are an imbecile). If you are not the leader, don't run off ahead when your leader is helping other party members get quest items that you have either already done or are too stupid to look at your map for. If your party members repeatedly ask you to slow down, or not to pull the boss until all adds are cleared, don't be a dick and pull a large number of mobs, kite them back to the group and AFK.