Hard to say without trying, and playing enough games to form an opinion on my end. Potentially very handy in FL.

One thing seems pretty sure though, it's a buff to crowd control jobs like WAR, RDM, SMN, etc. Even moreso for BRD and WHM who also have MP damaging abilities like polymorph or radiant, which will naturally synergize pretty wildly with this. Imagine you have to purify out of a polymorph, it's half of your MP gone.