I think Pitta falls into the category that nothing will be good enough. Losing Pettine was a bad deal for Buffalo, and possibly a worse deal for Pettine depending on how the issues with Cleveland fall. However, they didn't have much of a choice in the matter. Pettine took his guys with him. Pettine didn't run a traditional 3-4, so the argument about getting a 3-4 guy doesn't really add up. We have no nose tackle, Mario doesn't want to play OLB, and I'd hate to see him in coverage.
The Bills did the 3-4 experiment a couple of years ago, and failed miserably. No, I don't want a 3-4 guy. Pettine wasn't a 3-4 guy, what made Pettines scheme special was the exotic blitz that he drew up. We have 4-3 personnel. Switching to a true 3-4 would require completely revamping the defense, again. I just don't see what the problem is.