[Trexmaster]

Apparently God Rod will /always/ give you the full benefit of the effect, even if you don't have a staff weapon or you have Priest as your sub-class. (As in your FAI will /always/ be added to your spell power with Curate/Priest spells. I only tested this with Shine Ray and Holy Spark, but, I'd imagine it'd go for all the other spells.)

I tested this numerous times to confirm.

Dark Water also doesn't seem to affect the FAI stat at all (at least via Black Bubble--the item made tiles weren't tested.)