Cox changed the way the position is now played. That's a legacy
Really? I take it you never saw Peter Moore or even Jim Stynes play then? There have been mobile rucks before Cox and some bloody good ones. Cox was a very good ruck but to say he changed the way the position was played is putting serious mayo in it.
As far as Sandilands, my opinion is that while he has been very good he has somewhat underachieved when you look at his sheer size. He wins hitouts as you'd expect but he could be better at putting the ball to advantage. For the amount of ball he gets his hands on, he should have got more hitouts to advantage. Likewise, playing in an era where backmen aren't allowed to chop the arms in a marking contest he should have taken more marks. If he was a better mark he could play for another 5 years by standing in the goalsquare for 3/4 of the game.