Just out of curiosity, who do you see out there that would be an upgrade from the current 53-man roster? And who would you cut to make room for them?
WRT waiver awards, note the most active teams (Texans, Saints, Titans). Think it's mere coincidence those were also the top three teams picking in this year's draft? Anyone Houston puts in a claim for, they automatically get, and so on, and so on.
It's entirely possible the Bills put in claims on a few of those players -- we'll never know unless someone at OBD tells us -- but anyone of value isn't going to drop past the bottom five teams anyway. (I wouldn't have minded seeing them take a flyer on Michael Haynes or Rob Petitti, for example... but once New Orleans faxed in their paperwork, the Bills didn't even have a chance at them.)
As for the practice squad: except for Leak, Buffalo has an entire training camp/preseason's worth of tape on the players they re-signed. Again, unless it appears to be a significant upgrade, they're more likely to keep the players the coaching staff is already familiar with.
JMO.