First of all, the fact that the Buckeyes got into the playoff and lost last season shouldn't make a bit of difference. I've said this before, but one of the dumbest arguments I see every year, regarding things like March Madness or the CFP, is "So-and-so lost, so that just proves they didn't belong to begin with." News flash: every tournament game or playoff game has a losing team! The Buckeyes losing doesn't make the decision to admit them originally any less valid.
Now having said that, obviously any team that doesn't win its conference is going to face an uphill battle getting into the playoff. The Bucks had some good luck last year in that they had key arguments to make against their two main competitors, Penn State (better record, no blowout loss) and Oklahoma (head-to-head win). But that's not always going to be the case, as we saw in 2015.