The secondary is also very bad. I think it is important to know what is going on with JJ, Gordon and Stevenson. Those 3 have the traits to be above average players, with JJ being a blue chipper. Stevenson has not been on the field much despite fact that Wright and CJGJ have been getting torched (and don't have the foot speed to keep up with players in the roles being asked). JJ just has no speed right now - no idea if that is because of the injury and he needs an off-season to get right (he's still very young) or if there is something else there. Gordon - well - he has a history of soft tissue, when he plays he's very good, but you clearly can't trust his availability.
Brisker and Byard don't have a lot of speed either - so when you combine that with JJ (injured or not the same post-groin injury), Wright, CJGJ, and McCloud...that is a very slow and poor secondary. Combine that with an interior d that struggles to get consistent penetration and that makes for a really really tough job for any D. The ends aren't much better - but Booker and Sweat are solid players and Booker appears to be ascending. Difference makers - no (or not yet) but solid. Interior is just not good and shows poor discipline.
But when you add all of those together - that makes is real hard for any DC to do much more than try to figure out a bend but not break type of D. I don't think this is how DA wants to call it, but he's so limited in what he can do. They have a lot of work to overhaul the unit, but it can be done. I'm find sticking with DA as well - but wouldn't bat an eye if they did go a different direction, but I think the failures are not on the DC.