Rayik,
About the only thing RDM currently offers groups is Refresh II and Dia III. Everything else can either be done better, or looks cool but is otherwise useless.
CoolButInefficient
And when I say useless I mean they will have absolutely zero effect on the outcome of any group battle. You can remove them entirely and the group will still have the same results. Anything that ~might~ of had an effect on the outcome SE will make the monster immune to or otherwise incapable of being harmed by it. Even look at what they did to Saboteur, double the power of Slow II or Dia III was monstrously powerful, so they nerfed it (a 42% boost to everyone's attack made lots of NM battles a joke).
In fact I think that defines the RDM concept in general
CoolButInefficient.