I've been saying this for the past couple of weeks: Our overall numbers make us look like a bad defense, but dig into the situational numbers and we're slightly above average overall. For instance, we're currently 6th in 3rd down defense, 9th in adjusted pass defense, and 4th in power success (run defense on 3rd/4th down or within 2 yards of the end zone).
I think most people have correctly diagnosed half of the problem, pass rush, while missing the big picture as to why the coaching staff is ok giving up a ton of passing yards instead of taking more risk with exotic blitzes, coverages, etc...
Pete and Norton do not trust the safeties in coverage. That is why they've built the defense around the Tampa 2. In the Tampa 2, you are asking the safeties to cover the sidelines leaving the most important responsibility, the deep middle, to your best defensive player, Bobby Wagner. That's why people think Bobby doesn't look the same as he did in previous season, he's essentially the Earl Thomas of the Tampa 2, he's the safety valve in the middle rather than the hammer up front. Now, one of the biggest weaknesses of the Tampa 2 is the space underneath the corners/safetie's zones and the OLB's zones which where we've been exploited. Some people think that our linebackers are not doing great in pass coverage because there is often a few yards of separation between them and the opponent when they get beat, but that's a reflection of the QB/WR finding space between the zones rather than our LB's getting exposed.
Ultimately, the weakness of our defense is one that I don't think Pete and Norton foresaw being such a glaring issue and that's obviously the pass rush. If they can generate pass rush, then it becomes much harder for the offense to exploit the space between the zones because those routes are largely timing based. That is where we are at on defense. For the most part we're not giving up big plays in our base defense unless guys miss tackles, and offenses are slowly dicing us up because we don't have the pass rush to stop them from exploiting the only major weakness of our scheme. In every other area our defense is above average or great.
So one of two things need to happen for this defense to be elite, either the safeties (maybe Diggs) need to provide enough stability on the back end that the coaching staff trusts them in a wider variety of coverages, or the defensive line needs to generate more pressure to mitigate the weakness of the Tampa 2. Otherwise, we're a bend but don't break defense that is more or less a buffer to facilitate our offense rather than a force to be reckoned with.