I could agree with giving Rex another season to see if things start to turn around, but I do not agree with giving him an extension.
I understand all of the good things Rex has done in the past and that is why I support bringing him back. But the downward trend is very alarming and it does seem that he isn't learning to be more in touch with the offensive side of the ball.
The offense has always been where the problems have been since Rex is in town. The offense should be his primary focus. He needs to hire one his worst enemies on the field. He should hire an OC that always burned him or gave him everything he had to stop. A guy that has statistics to back up his success.
Then, he needs to LISTEN to the guy and go the way that OC thinks the offense should be.