Not only that but combine the invisibility / muffle spells with other master spells and your essentailly a nuke. I sneak into a pile of enemies, cast a blizzard, and BOOOM! A giant ass storm that rips them to shreds. Or mass paralysis and all of them are frozen stiff while I cast another spell with AOE. Hell just throw in a master illusion spell and bend the group to your will and let them massacre eachother while you run off on your mary way and recast invisibility and muffle again. Illusion just makes the world your [censored] essentaily. Remember some things aren't so easily fooled though.

But yes the skill tree does seem lack luster at first. Especailly with the low levels you read. However the perks up the level you can fool. And with duel cast the level crap increases even more! Dont let the illusion school fool you into believing it's useless. Because the opposite is ooooh so true.