I play on my dark elf, and everytime I cast a spell I think to myself, "wouldnt matter if I hadn't cast that spell". I end up switching from fireball to incinerate only to remember that takes only a pinch of a giants health. Destruction is like the least legit thing to have in your other hand. If your not dual wielding spells, then theres really no use. Unless you feel as satisfied as I do when you see a bandit ragdoll when you finish them off with a spell. Other than that, my enchanted weapon is way more practical than a spell.