I think the article posted by Seb V above quite expertly explains why Foley should be given a rest, and why he is not really performing at No 12. I think the author has a world of credibility more than the few Foley apologists who appear regularly on these threads.
Of similar interest, the section headed "The commitment to the Defensive Breakdown" probably explains why some of Forcefields' stats on the workloads of the tight five appear as they do. If Nick Bishop is correct, then it seems to be definitely a plan for the backrow, especially Hooper and Pocock, to hit the rucks with the front rowers and locks staying in the defensive line.