Milano will help, but he won't solve the issue. It's a scheme problem.
Buffalo will give up the runs to the second level. The problem is that if a RB can break contain on the 2nd level they can break off a huge run. Go back and look at the big runs, its almost always a clean hole where an RB can get some momentem and then run past a linebacker to the secondary and it becomes a foot race.
Its really just a trade off, big runs like that are rarer than big pass plays, and teams need more to go right for it to happen. Its frustrating, for sure. But overall success of the defense suggests its the proper decision.
I would argue that it is a scheme choice and not a scheme problem.
There is no defensive scheme that can take away everything that a quality NFL offense wants to do. The Bills defense is designed to take away explosives in the passing game first and foremost. That is why they have played nickel about 80% of the time, dime about 20% of the time, and rarely played with either 3 LBs or with a heavy box.
The Bills D is 7th in Points Allowed, 7th in Passing Yards per Attempt, 4th in INTs, & t-5th in fumbles recovered.
Because they play so much nickel and dime and they play so many light boxes and dare teams to run against them, they get gashed in the running game when they make alignment and/or run fit mistakes. But, that is the gamble they are willing to make in order to make it really hard to get explosive plays in the passing game.
They are making the bet that explosive running plays are rarer than explosive passing plays if they were to take Taron Johnson off the field and play a 4-3. Or, if they were to load up the box against the run on a more regular basis and give up more on the backend.
And even with all that, the Bills have only given up 6 rushing TDs this season (tied for 3rd fewest in the NFL).
They give up a lot of yards per carry (t-3rd worst at 4.8 YPC), but they have been good at stopping the run in the red zone and not giving up rushing TDs.
At the end of the day, I'll take a defense that is pretty good at taking the ball away, not giving up a lot of points, and has been solid when needed for the most part (red zone & second half).
Agree, it is not a scheme problem. It's a scheme design.
Buffalo's defense is very similar to the Tampa 2 defense from 25 years ago, Dallas' defense from the early 1990s, and the mid-2010s Bills defense. All those defenses featured a talent-heavy defensive line which valued single gap penetration to disrupt blocking schemes, and then a back seven which played heavy zone to read and react to what came of the line of scrimmage play. All of these defenses are derivatives of the 1970s Steeler defenses.
When you play that type of defense, you are committing to minimizing big passing plays but you can get gashed by a power running game if the runner hits the right gap. It's risk reward and you need to have a high level of talent in the front four.
Dallas overcame the run game deficiencies by rotating six linemen next to Charles Haley. Russell Maryland, Tony Casillas, and Tony Tolbert played on run downs, and Leon Lett, Jimmy Johnson, and Jim Jeffcoat played on passing downs. It also helped that Dallas had a possession offense which didn't turn the ball over and controlled time of possession.
Tampa was able to overcome the run issues in a bunch of different ways. First, they had 3 HoF caliber linemen in Warren Sapp, Simeon Rice, and Booger McFarland. Second, they were able to afford Derrick Brooks, John Lynch, and Ronde Barber on defense by being very frugal on offense. Third, Tampa ran a possession passing attack (Gruden's horizontal attack) combined with running from Mike Alstott to keep the ball from opponents.
The mid-2010 Bills had Mario Williams, Marcell Darius, Jerry Hughes, and Kyle Williams on their front 4. Maybe one of the most talented defensive lines in history, just part of a team that didn't win anything so no one remembers them.
If I'm the Bills, I don't think taking swings at a crazy talented defensive line or stacking the 2nd and 3rd level of the defense is the way to go. I'd look at a Dallas style line where you can rotate in talent. In the most recent mock draft I ran, I had the Bills taking Landon Jackson and Dontay Corleone in the second round, and Nazir Stackhouse later in the draft, because of my preference for this method.
In terms of defensive scheme and complimentary football, the Bills are fine. Brady is running a ball control offense, which when it is working, gets the Bills points while keeping the ball away from the other team (see the KC game). When you start to get into those types of games, the opposing offense gets down and the OC can get impatient. That will drive play calling towards passes, which is exactly what the Bills want.
If anything, I think Babich should be prepared to add in a traditional 4-3 alignment with Taron Johnson going to safety, in the event they are getting gashed by the run in the playoffs and the game is tight. Besides that, it's all working.