Our jumps have a cd of 90, 180 and 180. I think shoulder tackle has a cd of 30.
Going by that logic, if monk+bard dps is higher than drg+bard dps even with the disembowel buff, which it actually is, is there any reason to take a drg to a fight without 2 bards?
Mantra helps on big group damage and for creating a bigger succor shield if you're not nearly as geared to mitigate aoe damage such as megaflare. It might not be necessary but it still helps, and besides, even mages ballad isn't necessary for all the content if your healers don't overheal.