It's about 2-3 years too early to judge the Sabres tank, but they are looking good. Eichel is a star now and will be elite soon.
As for tanking in the NFL, the reason we say "it doesn't work" is because it's rarely ever done. There's too much money at stake. Besides Indy, I can recall a team in the last 10-20 years that overtly tanked. Of course, there were many horrible teams (Browns, Lions, us), but none of them purposely lost. Jets appear to be doing it now though, so we'll see...