Let's break some of that down:
Virginia in 06 and 07 had several bad quarterbacks. They rotated in and out when none of them performed. Supports the proposition that rotating QB's does not work and is generally a sign that you have insufficient QB play.
Virginia 08 -- Lalich was the starter until he was kicked off the team.
Cincinnati 09 -- changes were entirely due to injury. Pike was hurt and missed three games and was replaced by Collarros.
ND 2010 -- Matt is wrong here. Crist was the starter until he got hurt. Rees played a bit during games, but Crist probably 85% of the snaps. It still wasn't working. ND was 4-5 and struggling to score until Rees was named the starter by default.
ND 2011 -- Crist started the first game, sucked badly, and was replaced for the rest of the season by Rees, who got almost all of the snaps.
ND 2012 -- probably the best example of this working. Rees came in once due to injury to Golson, and then started two games during the season. Still, he only had about 15% of the passing attempts, not 49.
Tough to find anything here that supports the idea that splitting snaps evenly has, or will, work.