6-6 is a huge stretch. They still win all of their non conference games. Then lets say they end up in the east, they beat Vandy, Kentucky, Missouri, and possibly beat South Carolina. Depending on their draw from the west, they win 8 or 9 games. Still a top 15 team.
I'm not sure that Ohio State would have been able to hold up at the line of scrimmage. The few players they had drafted by the NFL should be indicative of the talent deficiency on their team.
Braxton Miller bailed them out time after time in 2012 against B1G opponents. I doubt he would have been as successful against SEC defenders with his offenisve line being abused. I have zero doubt that Ohio State would not have been a top 15 team if they played in the SEC.