All a matter of perspective and expectations.
I would say that, typically, a team that wins 5 games would be happy to win 8 games the next season, because its pretty hard to go from being a 5 win team to being a 10-12 win team in a single offseason.
However, that's mostly based on preseason expectations. Based on what we saw on the field throughout the year, we definitely left something to be desired. Too many games that we lost where we had a great opportunity to win, especially against teams that I didn't feel were as good as us (namely Redskins and Jets).
In the end, we beat some other average to below average teams, but struggled against the better teams in the league.
So if you take the season in a vacuum compared to last season, some significant improvements in some much needed improvement areas, and obviously a better record. But we could have been better, given our personnel. We were never SB level, but in a down year for the AFC, we could have won a playoff game or maybe two.