As I said, it sure seems to me that it is easier to have both, if the Head guy is an offensive mind. See OC's for Pete Carroll, Bill Belichick, Mike Vrabel, Mike Tomlin...Hell, even until recently John Harbaugh. It is highly possible I am missing examples one direction or the other, but not that long ago I broke down the list of HCs, how many were offensive minds versus the other way around. Not only were there WAY more offensive guys that made the playoffs, almost NON of the teams that made the playoffs had hired retreads. I believe it was just Reid and Bowles. The rest of the coaches had ONE HCing job in the NFL, and it was with their current team.
I guess Campbell is a defensive oriented guy, and he seems to have done a pretty good job of attracting and offensive coordinator. But there are sure a lot more examples the other way around. So, Mike Vrabel's offenses have been dogshit, but lets hire him? Dan Quinn coached a defense that just got run off the field at home against the Packers, but let's hire him. I don't get it. Two retreads out of fourteen, but we want a retread. Very few examples of defensive minded coaches having success on offense, but let's hire a defensive guy. Why fire Pete if we were going to hire Pete 2.0?