As someone with MNK BRD SMN and BLM all endgame geared (starting DRG relic now) I do think that DRG is fairly consistently lower DPS than Monk on any protracted fight. However, Monk is hampered from achieving its top DPS when it has to move away for more than a couple of seconds and losing GL3. So I think there is a parity there.

BLM is essentially idiot proof and is the top AOE damage out there (though higher DPS rotations like double/treble flares are a bit trickier and can leave you high and dry without MP for 5 secs or so) and among the top single target DPS (Monk can beat it on long fights). I think that this is always likely to be so because BLM is the iconic FF big-hitter. I think MP could probably be made to be more of a concern than it is.

BRD is an abomination to me in that it is barely a support class when it is usually the iconic FF (and MMO in general) support class. And their DPS, while lower than BLM/DRG/MNK on dummies, is unaffected by movement which means their DPS stays steadily high while BLM has to cancel casts, DRG has to withdraw from melee range for a time and MNK loses GL3.

tl;dr
Monk: Fine as is
DRG: Fine as is
BLM: Needs to be more MP-focused
BRD: Needs cast times or an outright damage reduction

These are of course unquestionably correct and I predict no-one will have an issue with any of these.