People kep wanting an Illidan redemption without realising there's very little to redeem. Everything that happened to him was of his own doing, he wasn't under the influence of a magical power or mind control or any such thing. He was a brat who wanted to play the hero because he was supposedly "destined for greatness" and too it way too far.
There is no epiphany at the end of his story where he apologises for everything he has done making everything right in the world, there just isn't.