RDM Disadvantages:

-is a caster, so will magic aggro. Magic aggro has a huge range.
-can't stun, so as DPS you can't work with your party to prevent hard hits while maintaining dps.
-lunges aren't as useful as you think, especially rearward ones.
-only role action to restore MP. If you die a bit it gets rough.
-you don't actually need that many raises in a party.

I mean, it's great otherwise, but other jobs work well. the big issue is melee, which seems to suffer a lot in content overall.