The defense faced fewer drives than the league average. In fact, 7 of the top 10 defenses in points per drive faced more drives than ours. Compared to 2012 on a per-drive basis, the defense faced more plays, and gave up more yards and more points. The average TOP per drive by opposing offenses was actually less in 2013, but that's mostly because teams were scoring so easily on us (one of the reasons TOP isn't one of the best stats).
The defense ranked 29th in 3rd down conversion % allowed, but when looking at conversions, there's no reason to focus just on 3rd downs. You're talking about a down that only accounted for 19.2% of all the plays that were run against our defense last year. If you look at all the plays, our defense ranked 32nd (dead last) in percentage of plays that resulted in a first down against them--that's plays run on any down. Our offense ranked 4th in the same category.
If I'm anywhere writing something football related, I'm usually here.