Lacy should be the primary back - don't think most would disagree there. More I formation and less shotgun would make him more effective.
Starks does a good job when Lacy comes out for a breather, or just to change it up. I think some people undervalue James and his contribution.
Harris is the most interesting back to me. I still don't understand why he is not used more in the gameplan. I think of him in a role like Sproles - a "do it all" type of guy. He is the type of back that can benefit from playing out of the shotgun - he doesn't need a large hole to make it happen, and he is quick to boot.
When I hear mention of Kuhn, I instantly think of his game against the Pats - he was phenomenal that night. When we need a tough couple of yards, Kuhn is the man for the job. He can block for another back, or he can plow forward himself to get it. I would like to see more 2 RB formations - there are endless options here, and they would get Kuhn more involved like he should be. He is a straight up old school FB.
These guys alll have a place in this offense - I just wish the staff saw it this way. They probably have their reasons, but one thing is for sure - it wouldn't hurt to get more creative with the run game.