I did some testing the other day with +piety gear on smn. The MP regen in and out of battle is directly tied to max mp/piety. So when i equipped all healing assesories it was a good bit of +mp regen. Obviously there was a dip in damage, around -25 per tick of bio2. So what i ended up doing was respecing my nexus since i had max det already, and +23 crit, i dropped the accuracy I had on there and threw on 22 piety. Seems to work out pretty well with no loss in DPS.