I'm not pro or anti-Daboll at this point; I'm will to give him next season with a known starter in Josh Allen and backup in Matt Barkley. This year, Daboll had four quarterbacks he had to work with, two of which were rookies: Peterman, Allen, Barkley, and Derek Anderson. Plus a patchwork OL and WR corps. Tough things to work with.
Tyrod was not the answer, obviously, but he had enough experience and ability to run an offense. Anthony Lynn got production out of Tyrod, yet Dennison could not. Denver's offense also regressed under Dennison. Peyton Manning's regression is an easy excuse, which I don't buy; Hapless Bills Fan pointed this out above. The point is, Dennison is a horrible OC and I don't think it matters who the QB is.