A good way to go about this would have been percentage-MP costs.
Like..one big heal is 15% of your MP. Still nerfing mages because MP costs are higher, but at least it's fair to any rank.
150 MP may be just 10-12% of your MP when you are Rank 50, but it's 100% when you start out as a healer.

Great experience for future conjurers:
"Oh, you want to be a conjurer? Just equip a wooden staff. You have 102 MP now. One heal costs you 70-130 MP.
You think that's bad and you feel useless? Well, people on Rank 50 are fine with it. How you get to Rank 50 with no or at most one heal? I don't know, but..have fun as a conjurer!"

I hope the dev team soon realizes how much they hurt themselves with that move.
Great job scaring newbies away if this stays until PS3 release