Tiote is our biggest liability at present along with Santon. I've defended him for a long time for the exact reasons you mention, last season and the one previous he was great for us. Yes he has always had disciplinary problems, but the difference was he could actually pass the ball and not get caught in possession constantly. So you took the rough with the smooth.
He has been absolute gash this season though. He can't pass the ball 5 yards and is giving the opposition 2 chances a game by simply being outmuscled and caught in possession. You can't pick teams based on assumptions, past reputations etc. We can't afford to handicap the rest with some warped sentimentality about him. He'll probably buck his ideas up as a result. you only have to look at the likes of Man U with Rooney etc.
I think it may just be complacency on his part. Not fickle at all by Tash, just an honest assessment of his current woeful season.