You are being silly if you think the Big12 of the last 4 year is somehow tougher than the Big12 from lets say
97-'05. You had Texas, OU and Nebraska who were all top 10 teams in the Big12. K-State was a power then as well. Over the last 4 year you got OU who is a top 10 team, that is it.
Im going off big XII as we had to play them now and then. We had the easy schedule and the tougher schedule. During Macs best years, Nebraska, kstate and Colorado were all slipping. The south took off around 2000 while the north was the weaker division then. So starting around 2000 we had the north 5 who were weaker than the previous 5 years and then throw on top of that, we alternated playing the three best and three worst teams from the south each two years.