Mmh, I don't see RDM anywhere, considering it's a really great DPS class for progression/casual raiding. But as many people will probably say it soon, play the DPS that attracts you the most. Only BLM and SAM seems pretty much shunned by the community, even though all class are viable at raiding. If you however wants to be sure to find a quick spot in any roster, play NIN/BRD/DRG.