Well I don't like the whole splitting carries thing I can see where the teams are coming from, They don't want the back to take to much pounding thus having his body fresh down the stretch. But then you run into problems with some backs that need to get the ball 20 times to get into the flow of the game. I recall hearing Barry Sanders say he needed to touch the ball alot just to get into the game. AP is another one that needs to carry the ball 20 times.
Out of the 3 you mention D Williams is the one I really wanted, I would love to have the backfield of Williams and Grant next year.
Also you point out yards per carry as the main stat, well that could be flawed also when you think Barber usually gets the ball on the short yardage plays. So when the defense knows your running it is kind of hard to have a huge average.
Just some thoughts, I am not saying we screwed up by not getting one of these guys, just saying you can't look at the stats.
I will try and do some searching,because I am interested in seeing how many teams actually have a shared backfield. Off the top of my head the 2 best rushing teams (don't quote me on the rankings) Atlanta and the Giants have a split backfield.
Just Imagine this for the next 6-9 years. What a ride it will be 🙂 (PS, Zero should charge for this)