Speaking of stubborn, Johnson would not let Groh hire any assistants. He let Roof hire Pelton, who Roof knew from Auburn, but that was it.
As others have suggested, after 4 DCs and 10 years of bad defenses, the buck stops at the top. Not only have there been consistently bad defenses, special teams are usually bad, and despite what some people say, recruiting has been worse than average by GT standards (and I am not necessarily talking about service ratings)--you have to go back to Pepper to find consistently worse (he also ran TO).
We have a good offense every other year, just enough to keep Johnson off the hot seat with just enough people. (FBS games-Yds per attempt last five years: 51, 10, 60, 19, 52). If things get really tough, he also runs off a scapegoat.
So look for a good offense next year.
How long will this go on?