I think you have to give them a little more credit than "truly mediocre". There are quite a few of those guys playing in the NFL right now. Or on rosters, at worst:
Coby Fleener (IND)
Toby Gerhart (JAX)
Stepfan Taylor (ARI)
Doug Baldwin (DEN)
Zach Ertz (PHI)
Tyler Gaffney (NE)
Chris Owusu (NYJ)
Toby Gerhart wasn't on that 12-1 team we're talking about. Stepfan Taylor was on that team, but a 5th round pick that has done nothing in the NFL isn't special. Same applies to Owusu... very mediocre player. Not bad, but not a great player.
Ertz and Gaffney were both not developed at that time. Gaffney also just isn't very good but that's neither here nor there. Ertz was a RS frosh who had 16 total catches.
Baldwin and Fleener were the lone "good" players on that offense. Baldwin is a mediocre NFL player, and for an ND comparison Will Fuller as a soph destroys his production as a senior. He went undrafted for a reason. The other leading target is Ryan Whalen who was a mediocre player (late draft picked, waived). Fleener was legit and was relatively developed that year as a junior.
So Fleener was the only regular starter on that offense who was drafted in the first two rounds. I think Michigan's corps of Darboh, Chesson, Butt, etc. is pretty darn comparable to that crop of Stanford players.