There's a lot to consider.
Is the tank a marathon puller in STR accessories perpetually stuck in their offensive stance, not popping CDs?
Are the DPS on par to handle the pull?
Are people standing in stupid?

It's 1 thing to expect the healer to heal. It's an entirely different thing when you expect them to carry.
Incompetent tanks/DPS will murder your MP usage and leave little time to do much else except spam heals and even then, if everyone is lacking and just eating every AoE then it's a group issue that needs to be addressed because healers only have so many oGCDs at their disposal to keep everyone up. I've let people that repeatedly stand in stupid die until they got the message that AoEs are bad and to hell with what they say about it.