Unless I'm missing how to do it properly buffs are a bit clumsy to use at the moment when you consider that your not going to want the majority of buffs permanently assigned to a hand. It would be better if you could also apply them directly from the favorites menu so that mid-battle if you want to re-apply one you can do so without having to then assign an essential spell to that hand.
If a disability is required and that's what this is intending to provide then simple making the buff take a few secs to apply would work.
Or give us back the wheel - that worked well IMO.