As WHM as well you generally don't have issues with MP management. It's only if the party really starts doing bad and wiping and you have to raise people often, or if you're doing a dungeon and the tank pulls large groups and then rushes off to the next one before your MP refills. You have a few different ways to refresh your MP as well during battle. I'm at level 60 but put it this way, having trouble trying to think of a time when I was full on out, it's VERY rare. I have like 13,000 MP right now at 60 and just iLvl 152 or something like that.