The defense is mediocre and improving. Its a big improvement from where we were last time at this year. Last year, the team was losing receivers down the field for long scores. Now they are losing them on the flats for 15-20 yard gains. The run defense was basically a 8 lane open highway last year. This year its actually . . . good. If you look at the actual runs that got yards, they were frequently long yardage situations. When its 1st and 10, Dallas isn't getting gashed like last year.
The Cowboys are going to get back Tank, Gallimore, Joseph, DT, Neal, etc. to add to the existing group.
Overall, I wouldn't be surprised if the defense ends up ranking around 10th once the season is done. That's an epic improvement.