I find illusion to be useless, along with alteration with the exception of candle light
alteration is useful if you don't use armor.
i had a sort of "monk" build i tried out for a while. character was kind of based on Li Mu Bai from Crouching Tiger Hidden Dragon. wore robes and used a onehanded glass sword. main skills were alteration, one handed and alchemy. sort of role-played the "stone-flesh" spells as meditation.
obviously acrobatics would have been useful for this build too, lol.
I don't think i've ever used candle light come to think of it.