I really do think you are on to something here. Defense was equally as terrible as it was elite in the 4 years. 2 and 2. The one year with Pettine was a D that was elite in terms of advanced stats only. The 2 years prior the defense was way worse than it was under Rex year 1.
I think the proper outlook is that the defensive personnel is vastly overrated by fans and are blaming way too much on the coaching.
If Ryan is going to go down and get run out of Buffalo by the casuals, he is at least going to do it his way.
Rex is going to be running the defense. Don't kid yourself.
I can't consider him elite but at the same time he is a player the Bills can't afford to lose at any cost. Also, Gilmore needs to focus on some fundamentals. Every year he gets hurt because of poor fundamentals while making a tackle.
He is going to do a post on the Bills in the near future to explain why. He says that in one of his most recent tweets. I'll make sure to get it in this thread.