What's your point? OSU and Notre Dame's strength of schedules are almost identical no matter which advanced metric system you choose.
If we're talking "more tough games," the team who really got snubbed is Georgia. I think they're probably the 2nd-best team in the country, but unfortunately for them they lost twice. The theoretical arguments about strength of schedule and saying things like "should've won" are fun to discuss, but in the end the point is winning football games. Georgia lost twice, so they're out. Notre Dame and OSU played comparable schedules, and Notre Dame didn't lose. They win that tiebreaker.
One could argue the merits of Oklahoma vs. OSU. They're both 12-1, and Oklahoma actually had an easier schedule still. What it all seems to boil down to is that OSU has (easily) the worst loss of any of the top 6 teams - so they're out there too.
What you're attempting to do (suggest that OSU should be in at the expense of Notre Dame) is silly. It's not particularly close. The more reasonable argument is OSU vs. Oklahoma, and it seems Oklahoma won out because of the "worst loss" factor - not to mention that they later defeated the one team they lost to.