Are you saying that once the ball is out (in the ref's opinion I guess), that a player from the opposing side can come from anywhere (there is no off side line) to pick it up? Surely that player would have to be onside at least until the ball is out, and probably called out by the ref if there's no half back in place.
What I'm saying is that in the picture in post #1011, that the ball is still in as it is between the legs of a player who is bound to the ruck. At this point, Michael Hooper is behind the last foot and thus onside. When we move to the picture at post #1015, the ball has cleared the feet of the last player who is bound to the ruck. The two players at the back aren't bound, so aren't part of the ruck, so their presence is irrelevant to offside lines. This means that the ball is out of the ruck and the ruck offside lines no longer exist, therefore Michael Hooper is not offside at post #1015 or 1011.
A ruck is a phase of play where one or more players from each team, who are on their feet, in physical contact, close around the ball on the ground.
A player joining a ruck must bind on a team-mate or an opponent, using the whole arm. The bind must either precede, or be simultaneous with, contact with any other part of the body of the player joining the ruck.
(c)
Placing a hand on another player in the ruck does not constitute binding.
16.6 Successful end to a ruck
A ruck ends successfully when the ball leaves the ruck, or when the ball is on or over the goal line.
http://laws.worldrugby.org/?law=16