The question is not really whether the Bills would be better off with a new coach. The question is THIS team going to be better off with a new coach, new coordinators, a new philosphy, a new system, and 2-4 years of adjustment.
I am by no means saying DJ is the end all be all....but I am saying continuity can ADD VALUE AS WELL. Look at some of the most successful teams in the NFL: Titans, Patriots, Giants, Colts, Eagles, etc....they've got the benefit of more than 2 yrs continuity at the coaching and QB positions. Look at the most unsuccessful teams: Lions, 49ers, Raiders. They seem to be just like us: a revolving door of coaches every 2-3 yrs.
Like I said, I don't think DJ is a great coach, but lets give it a little bit of time.