Disagree with the offense part. As an example, I consider Vlasic to be a legitimate #1D which you can win a Stanley Cup with. Johansen was more established as a #1C than Jones was established as a #1D (He isn't) so that deal shows that Columbus valued Jones' potential over Johansens track record.
Players like Seguin, Carter, M.Richards, Spezza, Johansen and others were traded despite being #1Cs. I can't even think of the last time a legitimate #1 D got moved (Pronger? Boyle?).
I disagree with the whole 30 teams = 30 #1Cs & 30 #1Ds. Yes technically players have to fill that role but I'm linking that position to a team looking to succeed. Some players are in positions that they simply can't handle.
#1Ds are harder to acquire/draft than #1Cs.
ppg was just a starting point, mostly because it was easy, and I agree that there are other considerations for dmen. I don't think Vlasic types are #1's though, guys like him and Tanev are very important players but they aren't the guys you put on the ice in PP situations or when you're down by a goal with 2 mins to play - I think your #1 needs to be able to do those things or they're only taking on part of the role (which I think can be done effectively with the right personnel, but if it has to be by committee then you don't have a complete #1)
Seguin I agree with but that was an instantly regrettable trade, Richards and Carter were an off-ice problem so I don't think their trades were hockey motivated, Johansen got dealt for a very good young RHD with huge potential who's close to fulfilling that potential.
PK Subban, Shea Weber, I'd call Jones one, Dan Boyle a few times in his career, Brian Campbell in his hay day a few times too, Brent Burns, Keith Yandle - lots of examples. Pronger I'd call better than a #1, he's a franchise type too
There are 30 (soon to be 31) of each of those jobs, so by definition the top 30 (or 31) guys are worthy of being #1's. There's a portion of the list that changes from year to year, so I agree that there's only a portion of the top 30 in each position that you'd be comfortable being your #1, but I counted at least 20 on each of my lists
#1D's are easier to draft than #1C's - Letang, PK, Buff, Weber, Yandle, Keith, Josi, Markov, Faulk, Parayko, Brodie, Giordano are all guys from after the 1st round. Many of those guys are near the top of the list of NHL Defensemen, multiple norris winners. Some of those guys are debatable as #1D's
the list of Centres from after the 1st round isn't nearly as impressive: Pavelski, Krejci, Ribeiro, Bergeron, Stastny. I think pretty much all of these guys are as debatable as #1C's, most are probably good enough but there's no franchise player here
I omitted the guys who retired in the last few years: Datsyuk, Elias, Lidstrom, etc
They're both hard to acquire for sure, but if I have to choose which hole I get left with I'd prefer the #1D spot, throw a ton of draft picks at it and pray - because it's easier to find them without really high picks