is it? What are some ways to boost it? Is it useful on adept difficulty or still worthless?
Your previous http://www.gamesas.com/topic/1456213-if-no-new-dlcs-how-will-they-fix-destruction/ contained numerous posts from people who did, indeed, find it useful - future patch or not.
don't know why they won't put a "fortify destruction damage by x%" enchantment, its much needed.
I don't use those as potions, and sell any I find.

Also don't use 100% magicka cost reduction items, or chug endless restore magicka potions, or do 100% stun lock.
Don't know why the previous posters said it was useful, I hardly see any damage to enemies past lv 40+
I find it useful enough that nearly all my characters have used it.
what difficulty is it even viable on?
I play on expert.