I think some of the moves Buffalo has done are a bit riskier than I would like. But, there is something to be said for taking that risk and being willing to give up prospects to get the players you want.
Myers looks like he might have a resurgence in Winnipeg, but would that have happened in Buffalo? Every season since his Calder year has been a disappointment from what I remember.
From my own perspective, the Caps for years had a lot of top-level talent and good prospects, but were always missing a couple pieces here and there that prevented them from going deep in the playoffs. Up until last season our depth on defense has been atrocious for all of Ovechkin's career. When McPhee was the GM, he was very careful about not giving up prospects - but this meant he never made the moves that could've pushed the Caps over the top.
Buffalo right now is stacked down the middle with Eichel/O'Reilly/Girgensons/Reinhart, and I really think Ristolainen is going to be a fantastic #1 defenseman. Lehner is still unproven, but he's very young and has already had some success in the NHL, and certainly has more upside than Lack/Talbot/etc. Buffalo still has a season or two where they won't be a contender and where they probably won't make the playoffs, and they should be able to pick up some more great prospects in the draft. They should be fine.