The Changeling is 200 points, has anyone used it to good effect? Halving the movement of an enemy could be useful, and knowing an enemy spell might also be useful but would immediately make him vulnerable. The only good way I can think of using him would be to have Tzeentch Disciples, redeploy him before the game, then unleashing the Purple Sun of Shyish right off the bat using Destiny Dice to make it nigh impossible to unbind (would need some 6s). And then he'll probably die after being revealed.
Is that worth 300 points?