How good a defensive team do you expect the youngest and least experienced roster to be? Half the guys that played every week were still kids or have very little games under their belt. Physical size, strength, and stamina plays a big part in defence. Team couldn't stop the roll of actual NRL teams.
Expecting any different with the roster currently assembled is naive. Club is still at least two to three NRL prop/middle forwards short of a forward pack to consistently compete in the grind during a game, and the season.