A lot people have asked the question of why some of us want BA gone, but are willing to spare DL. I've spent a lot of time reading, posting and thinking about the debates going back and forth regarding whether to blame the offense or the defense for the season failure. I think there's is absolutely a fair share of blame to go around. We won't include ST in this conversation, although we all know they get a nice slice of pie as well. But, people have been calling for Arians' head, myself at the forefront of them. While we do acknowledge the defenses role in the collapse of the team, this season, others refuse to see the offenses role in it. But, the reason people are calling for BA's head and not so much DL, is twofold.
Reason one is track record and resume. DL has a history of fielding top notch, championship caliber defenses, particularly in Pittsburgh, while BA has a history of running pass-happy offenses that don't necessarily produce when it matters most, save for 2008 season, and that's debatable. I'm a member of the "we won the SB in spite of BA" fraternity.
Reason number two, is the defense's problems can be attributed to largely to personnel issues, from injury to loss thru FA to incumbent players performing at levels significantly lower than in the past. Those are not schematic and philosophical problems. In fact those things will expose any possible weaknesses in the best of schemes. You fix that by changing the personnel, not by changing the coordinator. OTOH, the offense's problems were not personnel. They have a ****load of weapons, who were healthy for the most part, most of the season. Many of them had career years. The problems on offense were with philosophy, gameplans, situational football and playcalling. Those things fall squarely on the shoulders of the OC. And that has been his MO. To fix those things, you need a philosophical change. IMO, you usually have to change the person calling the plays to achieve that.
Hope that simplifies it for some of you guys.