I don't think Union is the same as league in terms of value of positions. Without the contest for the ball in League it is easier to hide players weaknesses, also the super structured nature of the game helps defensive re-allignments and set attacking structures easier to do.
I love my league (go Raiders) but there is hookers that can't pass either side, most of the players couldn't kick to save themselves and forwards play is largely interchangeable, hence the locking position now quickly becoming a 3rd prop. Essentially it's starting to become rather NFL like in that positions are defined (set players on set sides of the field) to a small set of skills that are conducted at an amazing level. Rugby players however need to be more rounded as there is multiple facets in which the opposition could exploit.