Definitely agree that the teams current success rate is unsustainable and a correction will occur over the course of the season. However, I do believe that Yeo has implemented changes to the style of play that compliment the Blues current skill set and that the success of the team is more than just an artificial bump after firing Hitch. The team is simply achieving better results with less (due to injuries and attrition) under Yeo than Hitch. How much did Yeo impact the development of Allen, or Hitch to Allen's struggles? Did he have a say in Brodeur's role or encourage the mentoring? What about Schenn and his chemistry with Schwartz? Would Dunn get a chance under Hitch? Would our defense put up 31 pts (14g) under Hitch? How much is the success contributed to the assistants and staff Yeo put together?
Head coaches don't do a lot of one-on-one player development, especially during the season, so you're asking questions that have nebulous answers, at best. Has Yeo had some direct or indirect influence on Allen's play? Probably...most likely through how the defense is playing in front of him, as they are generally doing a better job of controlling the top of the circles, the middle of the ice, and better job of limiting dangerous opportunities off the rush. Did Yeo have some sort of personal trajectory altering watershed impact on Allen's career? Probably not.
I don't think Yeo had anything major to do with Schenn's current success here. The professional scouts did a good job of identifying him as a potential fit, and Armstrong brought him aboard in a good trade. The rest is Yeo essentially not screwing things up by breaking up something that's obviously working.
Young players have been given their opportunities to shine under Hitchcock, so who knows how he would have handled Dunn. The Blues organization drafted him with the intention of playing him, so it's not like he wasn't going to get a shot at some point.
It's easy to say that Yeo's changes have had a real impact on the defense's offensive contributions now since the changes are obvious and those contributions are well beyond reasonable expectations. Yeo absolutely deserves credit for encouraging the defense to be more aggressive (something that I've been campaigning for a long, long time), and I do think that will have a beneficial effect for the offense in general and the team as a whole. At the same time, I'm confident that Yeo's tactical shift didn't suddenly make Gunnarsson and Edmundson (who account for 43% of those 14 goals by defensemen) 20 goal scorers. Pietrangelo is on pace for 25 goals. That's not happening, either. Parayko is on pace for fewer points than he had last year. Is that a mark against Yeo's system if we're giving the system credit for helping to facilitate outliers in the other direction?
The bottom line for me is that if the data sets you are using for evidence are full of numbers that you know won't hold up over the long haul, then it's too early to start making big picture claims about how much something is affecting something else, or how well someone is doing because of some other thing. The time to start analyzing that stuff is after the pendulum has swung back and forth a few times so you have some idea of where the middle ground lies, and then you keep on revising that analysis as new data comes in until there's no more new data to be had.
That's not to say we shouldn't talk about what has happened so far and give credit (or criticism) where it is due, and to respond to those things as fans with hope, enthusiasm, pessimism, or whatever.
It just means, in my opinion, that it's too early to be drawing long-term conclusions about Yeo as a coach and the hiring in general, and to be sweeping aside all the previous concerns that were out there about his hiring and the general future of this organization. The early returns are far more promising than I think many could have hoped for, but for all that they're still just early returns.