Yeah this is an underrated point. The reality is that PK probably had as much edge/LB talent last year as he normally did at UW, so why tf were the results so much different? Ultimately, the defensive staff (including but not limited to PK) just couldn't tie it all together. Sure, it was year 1 and a shift in approach, so I'll give them a tiny bit of slack for now, but no excuses if it continues.
So yeah, if the defense still sucks, it's on the whole defensive staff and the mismatched styles that Sark hired. Imo, the key to this year's defense is whether the position coaches and PK can get the players on the same page understanding the scheme and developing the mental ability to execute it. I'm blindly hoping that year 2 brings significant improvements in that bucket, but who the heck knows.
As mentioned above, S&C seemed like another huge culprit. It'd be interesting to see stats, but I feel like the defense was actually pretty good in the first half of games but just atrocious in the second half (with a few exceptions). The DL would start getting pushed around in particular. Have to believe some of that is S&C.