An escape goat to me is someone on whom blame is placed even though they are actually blameless. Mario is not blameless. If you watch he games you know this, he is part, maybe a big part, of the problem. His effort has been lacking, and this is not a recent phenomenon, it's been going on pretty much all season. The only reason he hasn't been benched is because the HC can't bring himself to drop the hammer. The HC may be problem #1, but Mario isn't far behind.
For Rex to have any chance at success, IMO, he has to be made to bring in someone to be the hammer. He also needs this someone to be a stickler for the "mundane" details of day to day business, and also be a strong game manager because Rex isn't these things. You might ask "then why keep Rex?" My answer would be that he isn't going anywhere so let's make the very best of his tenure that we can.