Apparently having more MP equates to using it more efficiently, too. Sorry, but RDM got by using brute force in the healing game, and even that would come crashing down in heavy AoE situations. Fancy that how the most preferred EXP mobs often had non-threatening TP moves to curb that risk.
With a good setup RDM hardly needed to cure at all in bird parties. Not even sure what you're trying to get at with that. Brute force had nothing to do with it.