1.7 was tied for the largest score differential Ohio State has had this season, the other being an early-season loss to Georgia. I would venture to say within one point is seen as competitive and 1.5 or greater is pretty substantial, but I am no expert. In the NCAA Championships, for example, the top six teams all finished within a range of 1.3 points. I hope this helps!
My interns neglected to inform me that yesterday was national sticker day, and thus I was unable to prepare a history lesson for you in advance. So it looks like we're going to be playing a little catchup.
Sorry, Kevin, it won't happen again!
fivethirtyeight also has the Buckeyes in the playoffs, this time edging out Notre Dame. But statistical models based on human behavior, especially ten people, can struggle.