Bards need a buff

[Akesis]

Bards ARE a DD role, but they have huge support capability. It would be unfair to other DD jobs with lesser support capability if BRD did equal damage. You have to give something to get something, that is the essence of balance in MMOs.

Bards also have the highest up-time of any DD and some of the highest survivability (due to having the greatest mobility). Again, are you willing to sacrifice those to have greater DPS?

If you want to get technical. Which, I can see that you do. Lets look at all of the DD jobs....

BRDs has 4 support abilities (Ballad, Paeon, Foe, Mantra). Can deal damage on the move. low multi target dps.
SMN has 4 support abilities (Virus, Resurrection, Eye for an Eye, Physic(healing as a DD is supporting the raid)). Can deal damage on the move. High multi target dps (if they don't insta-die).
BLM has 4 support abilities ( Virus, Eye for an Eye, Physic(healing as a DD is supporting the raid), Apocatastasis). They also have Atherial and can port to safety. Can deal damage on the move. High multi target dps.
DRG has 2 support abilities (Disembowel, Mantra). Can deal damage on the move. Can also stun. Middle of the road Multi-target dps. extremely high single target dps.
MNK has 2 support abilities (Mantra, Dragon Kick). Can deal damage on the move. Can also stun. Middle of the road Multi-target dps. extremely high single target dps.