Mage with Destruction (Impact perk), Illusion, and Conjuration. No crafting even necessary. There are four things Illusion won't affect: daedra, undead, automatons, and dragons. Daedra are really rarely encountered, undead are incredibly vulnerable to fire, and dragons can be stun-locked, as there are hardly ever two at the same time. A group of dwarven robots is the only potential threat, and even then with Twin Souls it's no biggie. And once you unlock Master of the Mind, forget about it.
What enemy is immune to casting invisibility? I can't think of a single enemy that I couldn't just cast invisibility "during" combat, and then sneak attack. You can do it over and over again. With enough magicka regen, it is ridiculously OP.
I'd love to see a mod that made casting invisibility only available out of combat.
Most enemies can still sort of tell where you are for a few seconds after casting invisibility, and quiet casting let's you go from assassination to assassination before you're even caught :D however, this class is weak against dragons, in my experience. They pretty much never just sit on the ground in a back stabbable position and are immune to calm spells...
Frenzy is great on higher difficulties, it is actually generally speaking a bigger source of damage than my destruction spells at the current level my legendary dif. mage is in, illusion is seriously overpowered, 20 sabrecats charging in on you? np, fear em away, frenzy em against each other. alot of people seem to be under the impression it's not that great, i've even heard many times it is ''only for stealth characters'' lol
Also, on legendary, there are alot of situations (generally bosses) where my direct damage spells don't do anything, various illusion spells help for crowd controlling when my companion/summon do the damage/tanking, and i can even buff them with courage spells to not have that ohh shit moment where they are down and suddenly you're the target.. Illusion has allowed me to put 0 points into health on legendary, i think that says enough