odds are that if the tank loses aggro it's going to be one of two classes. A healer, or a bard. Bards are considered by many to be the strongest DPS in the game, when their songs are not playing. The only reason you might want another dps over a bard is because bards lack a damage dealing limit break, which are necessary for some fights. Since end game content is usually 8 man raids however there is always room for 1(if not more) bard(s)