It is worth noting that Rennie has mostly been using his locks for breakdown work, freeing up others as ball runners. I see the problem more as a group effort than an individual one. So, as a group, they failed to get enough ball in the right areas of the field to get better metres. This, to me, is much more about their poor discipline, mistakes at set piece and ball control as a group (backs included) then the lack of run metres by Individuals.
That said, they do need to be able to chew gum and walk at the same time and the fact is that, across the board, the run numbers are poor and need to be better for each and every player (Valetini & Leota can probably get a pass for the game).
I am also a bit unsure why Arnold wouldn’t be seen as a primary ball runner, but it doesn’t seem to be how he is being used.