Lol. I wouldn't say it "worked", the Sabres still have a bottom 10 roster in the league.
If you're expecting ROR to be the 1st line heavy lifter be prepared to be disappointed, both times ROR was given that opportunity in Colorado we failed to make the playoffs and finished with the 2nd overall pick and 10th overall pick respectively. The two times I'm referring to are in RORs 3rd season, Duchene got hurt so he was given 1st line duty, and last year when Roy figured out that ROR can't produce on his own so he gave him our best wingers Landeskog and MacKinnon and then Tanguay when MacK got hurt. And then gave Duchene who can produce on his own Iginla, and a rotating door of crap players including McCleod, Caron etc.
Eichel is a kid, if you're expecting a 70+ pts year from him next year you will be disappointed. NHL teams will figure him out, just like they do every other player in the league. He'll have a nice rookie year but I don't expect him to come in and be a top 15 player in the league, and for your reference I don't expect McDavid to be there this year either. 2-3 years from now totally different story.
The defense that used to be scary, is not so much anymore with the losses of Myers and Zadorov. Buffalo's D is easily bottom 10 in the league right now. They are too young, they'll get better but next year will be a struggle especially if you're relying on Risto to be your top pairing guy. Most guys his age are learning the game as a 2nd/3rd pairing guy, asking him to be a top pairing guy is a ton especially since he doesn't have a workhorse #1 carrying him like Weber or Suter etc.
We are also talking about a team where the leading scorer from last year scored all of 46 pts. You added some nice pieces but, I don't think they'll magically transform the team into a credible offense force. ROR is a 50-60 pts guy, Kane is a 30 goal guy IF he is healthy and actually cares to put forth any effort, Eichel will probably end somewhere between 50-65 pts
Then you come to goalie and to be quite frank, I think you all made a terrible mistake trading a 1st for Lehner. Minimal experience, OK numbers. I think he'll be a big let down for you all. I wouldn't have given up more than a 2nd or 3rd for him. Much like the Talbot return from Edmonton.
Overall, I think Murray upgraded the team, but to say he pulled off a two year rebuild is pretty ridiculous. I fully expect Buffalo to be picking top 7 again next season. If everything goes perfect for Buffalo they may be picking in the 11-15 range. I don't think playoffs is reachable, unless everything goes perfect for them and some other teams don't play to their capabilities or have major injury issues.