I don't mean to sound pro-Ruff because I think his time has past like any sane Sabres fan. However, I have to disagree with the OP's reasoning.
Allow me to attempt devil's advocate.
Since 07, we've seen an excellent roster filled to the rim with heart and replaced everyone but the four mentioned with talented kids that have the potential to be great someday (Hodgson, Ennis, Foligno, Grigorenko)... older flash-in-the-pan guys that never really panned out (Stafford, possibly Leino)... average role players (Gerbe, Kaleta, Ott, McCormick)... and guys that debatably shouldn't even be in the NHL (Scott).
That's just the forward squad. The defense beyond Myers (who is having a terrible year so far), Ehrhoff and possibly Sekera... is riddled with vets certainly past their prime and fringe NHLers (or both).
This is a weak team. It has been a weak team since 07. You can talk about how the team has been changed from top to bottom, but changing good parts with average/lousy ones... then constantly changing those average parts with other average parts... usually won't make for a better team. How much of this really falls on Ruff? Maybe it's the coaches job to inject this team with life when they're down on the scoresheet, and make sure they're ready for games. Calm nerves between periods if a game is getting out of hand. Or maybe he's doing everything he can and the roster just doesn't have the talent/desire to back it up.
Is it shocking anyone that average players replaced with average players are still playing average hockey?