Dahlin and Power they had no choice to draft them. You don't trade down when you have the 1st OA pick and they were the concensus #1 picks.
Having too many centers is rarely an issue...on the wing they traded for Tuch and drafted Peterka, Quinn and Benson...all look to be legit top 6 wingers. They also drafted what appears to be their real #1 goalie in UPL.
Sabres have sucked for so long they are stacked everywhere. If they need a RD they can trade for one any time.
With Byram they picked the best young player offered, that's better than trading Mitts for a significantly lesser RD just because you need a RD.
Dahlin, absolutely you draft him. All the other LD are debatable.
Without a vision for a team, you can't build towards anything. They have kept buying lotto tickets over and over and over. Hoping that they will eventually fit together.
Part of having so many assets is you simply don't have space for them. If you have 4 1C prospects and you wait 4-6 years for them all to mature, at some point in time, these players will have questions. They may not establish at center, which destroys their value. They may have questions on ultimate upside and people only see them as a 2 or even 3C. You start having declining value over time and you actually have to start pulling the trigger.
Power is honestly a great example of this. They could have traded down for a haul... or traded him prior to his new contract for a haul. Now teams are naturally going to wonder if he really is that sure thing #1D. If they moved him today, it would be for far less than what that #1 pick was worth or what he would have been worth prior to the shine wearing off.
Even Byram certainly had some shine wear off. If the Avs trade him right after the 22 Cup, he brings back far more than Mitts. Hell if they even traded him last summer, he would have brought back more. The time let more questions show up, and Byram never grabbed the role expected. If you do that with a bunch of different players at the same positions, eventually the value declines.