I constantly see this argument that the D has been terrible for years. Yes, there were plenty of games under Bo where the D was absolutely terrible, but it wasn't "every game". The problem with Banker's D is that EVERYONE has had big games against the Banker D this year. Almost every opponent has gained more yards against Nebraska than their average total offense for the season. I am not sure where it is in the "scoring defense", but I am sure the past 3 opponents have scored more than their average. Purdue scores 55 against NU in one week, and then 10 points against Illinois the next week.
Yes, Bo had complete failures against Wisconsin twice, UCLA, and a few other games. However, with Banker's D they are a complete sieve. Against Michigan State, the Spartans went FG, TD, INT, TD, TD, TD, TD in a span of 7 possessions. That's not good.
No one is going to argue that its good. There is lotsa of work to do.