Mages fury currently increases offensive wpa by 10% while decreasing defensive wpa by 10%. But with wpa, 10% either way is hardly noticeable. Also, mages fury costs mana and runes, meaning it is not even worth casting it if it doesn't at least lead to two successes in a single casting run that would have been fails without it. I doubt 10% extra offensive wpa is worth that. Similarly, the 10% lower defensive wpa is not that much of a penalty.

So make the spell stronger. How about both 30% higher offensive wpa and 30% lower defensive wpa? Then it makes some difference, while also seriously opening the mage up to enemy spells.