http://www.gamefaqs.com/boards/615803-the-elder-scrolls-v-skyrim/61133373
Seems it only affects fire damage. I was thinking hypnotic gaze or rage might buff ice or shock but this is NOT the case it appears.
Sorry if this is old news but I only just found this out (all cred to other people of course) dont believe its working as intended... I mean Illusion perks buffing Destruction? Dont seem right to me...