Not my answer but perhaps you didn't see it:
Melee power stance, rage and oath all effect spell damage. You will need a melee weapon to activate power stance so you need a staff or dagger/wand (for a pure mage ofc). Dagger needs to be in the main hand and requires dex so prepare your tormented souls. Also not all spells stop scaling at the same time. Check end game spells like ice hail to make sure the int scaling has stopped.
