This is quite a nice boost for any out of combat buffs that you cast, even ignoring Persist Spell. Being stunned for three rounds when you are in a safe place is a not-a-drawback. Instead of spending thirty seconds casting your breakfast buffs, it takes about two minutes. No one is going to notice the difference in prep time.
It does have a less than optimal prereq for a caster (who probably already has a good will save), but if you need Iron Will for a PrC anyway, there is no reason to not take it other than all of your feat slots are already allocated to even better feats.
It does have a less than optimal prereq for a caster (who probably already has a good will save), but if you need Iron Will for a PrC anyway, there is no reason to not take it other than all of your feat slots are already allocated to even better feats.
