My question is, is it worth using over Inner Light or Evil Hunter?
Depends on your build and what you want, really. The damage from Inferno really isn't great enough to be the difference in a fight. Plus, Evil Hunter and Inner Light both do more as skills. Magicka builds would probably want Inner Light for the increase to max magicka. If you're only interested in crit, I would go with Flames of Oblivion, morph of Inferno, because it gives both weapon and spell critical. I like having one skill that does both.