Skinning problem, Cannot Alpha in Areas

I've tried everything. I've read previous post and ect, but none really clearly states my problems My problem is that I can't alpha in certain parts of the assassin. I'm trying to take the coat of completely but have remains of the shoulderblade sticking out. Please tell me the way of fixing this

Some models are not able to have certain pieces alpha'd out. The warden is a popular one to use as an example. No matter what you will need a model edit to change the wing things on her back. I believe her cape to. There are more models but thats the easiest example i can give.