The wild card with Rex is, from reading "Collision Low Crossers", that his heart can interfere with his head when it comes to personnel decisions. It was clear from the book that Rex would become emotionally invested in certain players, overriding objective assessment of their talent. Rex stuck with guys way too long and other coaches on the staff began to question it.
So, I guess given that information, it's not an either/or proposition when it comes to believing in this staff or not. I believe in Rex's ability to judge talent, but maybe not so much his ability to make objective performance-based personnel decisions.