I would put us in or close to top-10. We definitely have a better defense than:
Ottawa
Vancouver
Detroit
Pittsburgh
Edmonton
New Jersey
Buffalo
Philadelphia
Anaheim
Chicago
Montreal
Los Angeles
Winnipeg
New York (R)
Florida
(15 teams)
And I would argue we have similar or better defense than:
San Jose
Nashville
Columbus
Washington
Calgary
Arizona
Dallas
New York (I)
Boston
Colorado
Toronto
Vegas
Minnesota
(13 teams)
The only teams that have definitively better defense are:
Tampa Bay
Carolina
(2 teams)
Our Top-4 is pretty strong. Just a little while ago, it was best in the league, or at least third-best.
Pietrangelo > Parayko
Parayko > Faulk
Bouwmeester = Krug
Edmundson/Dunn/Faulk = Scandella
Gunnarsson < Dunn
Bortuzzo = Bortuzzo
I don't think we majorly downgraded in defense, and I'm a person that was very down on exchanging Pietrangelo for Krug. This team's defense is still very good, just not league best anymore, and I think the differential is what makes most fans think it's much worse than it is. That, and our defense has been more about offense than shutting down the opposition. Bouwmeester was great to shutdown our opponent, but his offense was a blackhole. We're one top-pair LHD from having the best defense in the league; without it, we're still contenders.
Our forwards MAJORLY upgraded, though.
2019
Schwartz Schenn Tarasenko
Blais O'Reilly Perron
Maroon Bozak Thomas
Barbashev Sundqvist Steen
2021
Schwartz Schenn Tarasenko
Sanford O'Reilly Perron
Hoffman Bozak Kyrou
Sundqvist Barbashev Thomas
I think I would take this team over the cup team, though it would be close (I'm a very big Pietrangelo fan).
Montreal and Florida deserve to be at least in your 2nd group and arguably in the final group. Maybe they regress, but both of those blue lines have been squarely top 10 this year. Both might be top 5. They have both been fantastic and while you can argue that our blueline is constructed better, we have not played nearly to the level they have this year.
Montreal is 1st in the league in xGA per 60 (5on5) , 2nd in actual GA per 60 (5on5) and top 10 in just about every defensive metric. The only metric where they fall outside top 10 is raw GA per game and PK%. Which is understandable with Carey Price sporting an .898 and still starting the majority of their games. Petry is 2nd among D men in goals, points, and +/- this season. He leads the team in scoring, so it is pretty safe to say that the blue line is dragging that team along this season. Weber has 10 points, which is 1 shy of Faulk.
Florida has been amazing defensively this year 3rd in xGA per 60 (5on5), 7th in actual GA per 60 (5on5), 1st in high danger chances against (5on5) and are top 10 in pretty much everything. Like Montreal, their only area of struggle defensively is on the PK. Lo and behold their starter is sporting a .900. Ekblad leads NHL D men in goals and is 12th in points. Yandle is at 16 points, which puts both guys ahead of Krug on the scoresheet. Weeger also has 11 points and is proving that his 30+ point pace performance as a legit top 4 D man last year was no fluke.
We are 9th in xGA per 60 (5on5), 19th in actual GA per 60 (5on5), and 13th in high danger chances against per 60 (5on5). Overall, we are 22nd in the NHL in GA per game and the PK is 25th. Binner's .908 is noticeably better than Price/Bob's so it is tough to write off our poor PK number as the goalie not being able to make a save.
Montreal and Florida's blue lines are contributing to the offense as much or more than ours and they are defending a hell of a lot better. I think Parayko returning at 100% fixes a lot of our issues, but we aren't on par with these two teams unless he comes back looking like the top 20 NHL-Dman has been in the past.
I ultimately agree with you that we are in that our D is in or near the top-10 when healthy and I think our numbers being below average are largely due to Parayko playing well below 100% (and now on IR). However, the on-ice results haven't been great so far. The Krug-Faulk pairing has been way better than I expected, although they seem to be regressing to the mean a bit right now (which still leaves them squarely as an above average top pair). Dunn/Bortz have good underlying numbers together but haven't translated that to actual results yet. Scandella/Dunn have been okay, Mikkola is getting caved in regardless of who he plays with and we'll see what Scandella/Parayko are long term.
Edit: I have watched a lot of Florida this year because I have chosen Driedger as my yearly fantasy pick for "goalie I think will outplay the established starter." They rarely play at the same time as the Blues, so I have watched a good chunk of their games. The stats above were sought out in support of my eye test, not just because they look good on natural stat trick. Same thing to a lesser degree with Montreal. I always end up watching them a decent amount because Price is otherworldly when he is on his game. The additions of Eddy and Allen have made it even easier to root for them this year too.