Not only was Hall's career on the downslope but not long after signing with the Roosters he tore his ACL and had to complete his rehab in Australia. Then after he got a few games under his belt, he went on tour with England where he dislocated his knee and had another injury plagued pre-season.
Still, to play alongside all those talented players and come up with a goose egg is telling.
I think there are a number of reasons why the English backs tend to struggle in Australia. You touched on one and the choice of club certainly plays into it. Another factor is that they rarely last a season so they never get that opportunity to sharpen their skills and pick up on the nuances that are required at NRL level. The other factor is that England are just lacking those top end James Tedesco, Tom Trbojevic, Latrell Mitchell, Joseph Manu etc. freak of natures.
I'd imagine that's because anyone who is athletically gifted is steered towards Football or Rugby.
Still, as we've seen with Farnworth and Young, if these players are given time to develop they can be quality players in their own right.