I actually don't think the problem with RMD or Godcomp is the mage or the rogue. Its the druid. Every other healer has to cast, doesnt top their entire team with instants that heal more than the casted heals of the other healing classes. The mage/druid combination is insane too, cause of the fact druids provide so much durability for the mage and they can rotate their CCs.
Everytime I meet RMP it's doable, but when its a druid, its on another whole new level.
I can't even imagine how bad godcomp would be with a paladin or a shaman healer LOL.
Honestly, it's just druids. I don't think there is a single comp in the game right now that's not better with a resto druid healing it and not some other healer ( except maybe LSD2).