Dirtii is right. The skinning macro relies on the fact that the main/focus can target the corpse and this allows the follower to target through them, herbs and nodes cannot be targeted and so the macro won't work.

Personally I do like having one of the two minimap based gathering professions on my main anyway that way I've got them displayed on the minimap on the primary screen- saves me either checking follower's screens every few seconds or missing valuable mats.