I can give you that...perhaps I did overbuy and there is a good chance that a large majority of the fan base did as well. I say chance because I don't want to speak for all of them.
Crazy enough, there is a large difference in perception when it comes to 8, 9, and 10 win seasons. 10 seems to be what "great" coaches are measured against, the number of double digit wins. I think subconsciously we all want to get to double digits when it comes to adding in the bowl game.
The first year, I was thrilled with where we were. The second year, the way we lost left a very sour taste in my mouth, but was happy with the progress we had made and the understanding that we were building for the future. Last year was indeed a dream season, but anyone that understood sports, as you have pointed out, knew that we were good, but not great/elite, and had some very fortunate bounces that helped along the way (and you need those in order to be successful).
In year four, I was not looking for a team that has an identity problem. You know how to practice, you know the system, there should not be any issues with who or what you are. The expectations were built in by Kelly himself, in branding the BCSNCG into the schedule and talking about winning championship (this was after Rees became starter, and I understand that it is coach talk). Four years in you expect a "succession plan" for the talent you know that you are going to lose, and expect those guys to fill in. I never imagined our D being this bad, and certainly did not expect our offense to be unable to be consistent. Not four years in. Year one and two, yes, but not when you have established your foundation.
That is where I think Kelly "oversold" us...the expectations that in year four we would be a consistent winner with the "Next Man In" mantra...and it has not, to date, been the case.