Although last season our back four was mostly, Muscat, Dura, Siggy, Fenton (and a bit of Doyle) and it was only 4 goals away from being the best in the league.
One of the reasons I don't think the personnel at the back is the issue. Last season the Nix were consistently on the front foot with majority of possession and constant pressure in the front third. This year we consistently turn over the ball in the midfield close to our goal without being able to transition to attack, opponents winning the ball and able to free it into space bypassing the midfield while the defense are still scrambling.
Fix the impotent front third and you'll see a much improved defensive effort.