You see far more of Burgess than I do, but he was starting to go really well in the NRL at the end of last season. He joined the wrong team in the first place in the Roosters, but it took him a while to adjust to the physicality of the NRL. By the end of the season with the switch to Souths he looked far more comfortable - particularly on kick returns where he was far too easily pushed back at the start of the year.
Eden by contrast never looked anything other than a lightweight in the NRL. He did't get many games for the Broncos, but the ones I saw he lost every collision and looked likely to drop the ball every tackle. Hardakaer looked just as weak for the Panthers, but had the 2015 or 2017 version gone over may have done better.
The NRL is just more physical for backs than SL, and whilst most British forwards adjust, our outside backs seem to struggle.