I disagree with your premise here. Our last national championship team (which wasn't THAT long ago) essentially played 6 guys most of the season. Casey Sanders got some minutes at season's end as Guy #7, but only because of an injury. There is no magical number of points that the bench has to produce for a team to be successful.
That's not to suggest our front 6 guys this year are comparable to JWill, Battier et al, but frankly depth is overrated. It's nice to have in case of injury or foul trouble but it's not a deal-breaker. There really aren't enough minutes to go around for more than about 8 guys.