College Football Reference uses a “simple ranking system” indexing point differential with strength of schedule. By that metric, this last year was the best Illinois team since the Nate/Leshoure/Martez team in 2010 that beat Baylor in the bowl game.
They played the toughest schedule since 2005, Zook’s first season. CFR actually ranks Illinois’ schedule 9th in the country. SoS rankings vary in method, but a brief survey across a number of different sites all have Illinois in the top 30 this year.
As others have already pointed out in this thread, the year to year improvement in defense was amazing.
As much of a roller coaster as this season was, it was overall a pretty decent first season for a new coaching staff.
Onward and upward.