This defense is completely different with a healthy Dennard.
The ripple effect is huge. Arrington, especially banged up as he currently is, has struggled on the outside to the point of getting replaced by Ryan &/or Cole at times. When healthy, and I'll assume by January he will be, he is as good a slot corner as there is in the league. Adding Dennard boosts two positions, tremendously.
Our run D will continue to struggle, but we might be lucky and avoid any good running teams in the postseason. When we've had our top 4 CB/DBs healthy (Talib, McCourty, Arrington, Dennard) - our secondary has been a strength of the team.