Actually both happened. Auburn brought in Lindsey this year and their defense is great this year.
Lindsey might be calling plays but Auburn has not changed their scheme imo. It's been tweaked a bit due to personnel. CPJ tweaks his as well. And it's obvious whether you acknowledge it or not.
And yes Auburn has a great D this year. Imagine how our struggling O (this year) might have looked paired with that D. Probably a good bit better.
What does Auburn's D have that we don't? Future NFL Dlinemen. High picks to boot. If we hired the Auburn DC at the end of this year would he get the same results with our guys?
Maybe Roof isn't the right fit. Maybe a different DC could recruit better, coach and scheme better. I would be surprised if the results weren't similar though, either a little better or a little worse possibly.
The Dline has actually improved in the last 3 years. From pretty bad to somewhere around the median. Next year the DL will be a bit better. Still not likely to be elite but will be improved again I think. Even fairly marginal improvement on the DL can make for a fairly big difference in this game of inches. So I think the D will improve overall again next year whether Roof is the DC or not.
What we most have to improve on, as always, is recruiting. Hopefully the school will fund that endeavor competitively moving forward. Lord knows we probably need to find it twice as much as our competition to overcome our built in obstacles.