Think about this. a Healer running out of MP is a VERY bad thing. So we should actively try to avoid letting it happen. Since healing is the primary role and responsibility then doing 'other actions' will be the first thing to be sacrificed. That means that by nerfing the mp efficiency, you're really just limiting our chance to do something 'other' than heals. The MP efficiency is there because our primary limiting factor is GCD/Cooldown/Cast time, not 'MP Resource Management'.
I mean, if I'm being honest, the only reason I run out of MP is if I'm being too aggressive on my offense, not my healing.
