ruck stocks are an interesting concept.
The theory of having 4 spots on a list to cover that one spot is difficult cos essentially you're no1 ruck will get most of the game time, you're no.2 has to accept his spot and role and do his best when needed, and spots 3 and 4 are there for developing players.
However in any one year pretty much no matter what, if ruck 1 and 2 go down, you're screwed anyway. Look at WC, soon as nic nat went down, they were screwed.
If gach was doing all the right things off of the field, then his delisting seems odd, as you wouldn't be expecting him to break into the side for another 2-4 years so the expectation of him wouldn't be that great, and his ego essentially wouldn't be dragging him off to another club if he was able to show some promising signs.
Not a bad delisting by any stretch, but eh.