While I agree with the gist of this, why are you mentioning Scandella at all in this post? He played in 20 games this season - playing his first game on Feb 21...
Basically, he was nowhere near game shape until after the trade deadline, and playing about 90s below his career average of 19:37 a game (17:50 aTOI) finishing +2.
In essence, once Scandella returns coincides with when our team stopped getting caved in on a regular basis defensively... Our top 4 looked passable once Marco returned.
My post is about needing a legitimate top pair (or really good 2nd pair) caliber LHD in order to make the top 4 group here work as a genuinely good defense. I don't think Scandella is that guy, which is why I brought him up as not being that guy. Regardless of coaching/structure changes, I don't expect the D to be above average if the top 4 is Parayko, Faulk, Leddy, and Scandella.
We allowed the 11th most goals per game and 8th most shots per game after Scandella's return. Scandy only played 15:19 a night at even strength, which isn't close to what you need out of a legit top 4 D man. He played 15:56 a night at even strength in 2021/22. I'm far away from the "blame Scandella" bandwagon, but he's a #5 (who can sub into the top 4 for stretches) at this point in his career. He hasn't been a #4 guy in two years and he's 33. I think the odds of him playing like a #2 or #3 D man in his age 33 season are pretty damn low and that's the thing I'm talking about needing.
Like Krug, I don't believe that he is capable of being playing a legitimate top 4 role on a team that is trying to succeed with a 'death by a thousand cuts' strategy in the top 4. he could probably be the 'stay back and cover the zone' guy for 17-18+ even strength minutes a night alongside a Fox, Makar, Heiskenen, etc but we don't have one of those here so we need more than that.
My ideal roster construction sees us bring in a top pair (or extremely good 2nd pair) LHD, moving Krug, and keeping Scandella for the bottom pair (and likely top PK unit). Scandella playing 12-15 minutes a night at even strength gives you the backbone to a good 3rd pair that doesn't need to be insanely sheltered. He can genuinely help the team in that role if you can make it work against the cap. I don't believe in the 'addition by subtraction' theory with Scandella. but the top 4 needs a LHD man better than him. And unfortunately, Krug's contract might be difficult enough to move that Scandella is the cap casualty to bring that upgrade in.