I would have just gone with winning % and whoever gets 1st seed gets 1st seed. Bengals weren't realistically getting that anyway, so you're talking about the difference between #2 and #3 seed for them.
Bengals win their division and clinch #3 at worst. #1 seed comes down to Chiefs/Raiders and maybe Bills/Patriots (if Raiders win).
It would have made more sense (IMO) to do all the above and IF it came down to Bills/Bengals in the Divisional round play that game in Cincinnati, regardless of whether Bills or Bengals are #2.