Bard's damage isn't that much worse and often times, better, because to do better, you have to be a really good player.

An average caster/melee isn't going to outdps a good bard. But a good caster/melee could.

I'm almost always top dps in trial roulettes as a bard

I'm not even the best bard around. There are bards at the same ilevel as me that can do 10-20 more dps.