I don't really care about DVOA rankings and very few people do. It doesn't explain WHY they are what they are. It uses a million different scenarios which are rarely trends or actual statistics, and even includes pre-season-based calculations. Strength of schedule for example. Something that is a pointless word thrown around and means nothing on each and every Sunday or each and every year. You could have just as easily pointed to points allowed and said we're 28th. It's the same argument.
It doesn't take a freaking mathematician or analyst to figure out we are a team averaging 416 yards per game, but our points don't equal up to that number. We should be averaging 30 legitimate points and we only did it once.
Team DVOA is not based on preseason stats or strength of schedule.
The whole purpose of DVOA is to determine how a team is performing compared to the average performance. When compared to the average NFL defensive performance this year, the Panthers rank last.
You can use whatever stats you like, but clearly the defense is not performing. At all. If you want to pick on the offense, thats up to you.