Ehhh, I went to a bismarck ex group the other day as a bard... I was doing 15% more dps than the other dps, and I was in the worst gear. Bards can do some decent dps too!
I guess our mages ballad is good for keeping the party alive, when it provides MP for the heals. If people are alive, they can do damage. The foes requium also boosts the dps of mages, so I think overall it balances out.