I think Buffalo could beat the Chiefs we saw today, but I don't think they could beat the Bengals we saw last week... well, they didn't.
Buffalo has a few more years of prime if they can keep their team together. I wouldn't worry too much. I know it's been a long drought for Buffalo, but they still have time.
It's just like San Francisco today who played the Eagles. On paper, the 49ers have been a better team this year, but then their quarterback got injured and they had a backup in. Today they scored a pathetic 7 points when their average score is toward the 30s. It's unfortunate, but that is how football is. Opportunistic.