From what I've seen since the DRG buff, A perfect Monk vs. a perfect DRG will do nearly the same dummy dps, but due to even the smallest portion of unavoidable mechanics DRG will usually slightly, slightly outdo the Monk. The Monk also brings mitigation, which is unnecessary after a certain amount of health (usually ~i123 or so for Bard, etc.), while Ninja bring at best 10% more damage 1/6th of the time (or 1.67% bonus raid dps), and Dragoon brings about +8% more dps to the Bard (won't effect DoTs, but will effect SS, HS, BL, AA, oGCDs), who will already be your lowest dps. In FCoB fights, Monk seems to have the most gap from dummy dps among the three melee dps, more significantly in a couple (T11, T13).

If your raid is doing about 580/570/560/500(Bard) across dps, and about, say, 2800 dps overall, Ninja will give 47 more dps, the DRG will give 40 more dps, and the Monk gives... at that point probably barely-unnecessary mitigation, but might save a Medica/Succor each major AoE. That all seems pretty close to me.