What if we changed Presence of Mind to allow WHM to move while casting for 20 seconds instead?
Question, how would you cancel your spell? I say that because most players would just move slightly to cancel spell casting, but if it continues when you are moving then you could be stuck seeing it through to the end. Maybe you started casting Raise but someone else beat you to it, ideally it's better to cancel if it's possible to save wasting MP.

WHM has a few nifty CDs though so perhaps movement isn't the biggest issue at the moment, if Presence also boosted/effected stats in some other way (damage up, stronger/wider Benison etc) that could be a good start.