RDM/NIN isn't used in parties. It's pretty much only for soloing. As a RDM, you should be using /BLM and /WHM as your subjobs.

And yes, a RDM's main role in a party is using magic -- enfeebling the mobs, refreshing the mages, hasting the melee, curing when needed, etc. With everything you have to do, there's hardly any time to melee anyway.