I think a bigger problem with the inconsistency is the relative youth on the team. Sure, this team has 3 seniors and a junior, but BYU is also relying heavily on 4 freshmen in Emery, Seljass, Chatman, and Hartsock, as well as a sophomore in Corbin Kaufusi who didn't even originally intend to play basketball in college. There's bound to be more off nights with underclassmen, particularly later in the season when it's a grind.
I also think Rose's run-and-gun offensive system does not work well in the WCC. BYU's half-court offense is below average, even by WCC standards, which equates to fewer open, in-rhythm shots.