I can't post on the US forums, thanks Blizzard, referring to this post: http://us.battle.net/forums/en/wow/topic/20749088056
There are first reports already, that people who got 2-3 legs during the bugged "luck system", already got another one. This suggests my theory how the luck system worked:
You open a chest, got no leg, luck counter + 5 (imaginative value) for example.
You open a chest, got leg, luck counter accidentally also added a value, for example +1000 (imaginative value), instead of subtracting it.
Mostly the guy who programmed this part just got lazy and programmed it all + instead of the one - (leg drop).
So your chances of getting another leg was now 1005, instead of 0 again (you obviously can't get below zero).
So people who got 2 legs were in their 2xxx luck bonus for example, who got three, 3xxx.
And now comes the thing: I totally guess Blizzard didn't clean up the database, it would be too much work to identify who got a leg and then argument maybe it wasn't bad luck at all. They just hotfixed that getting a leg will subtract your luck bonus counter instead of adding to it too. What does this mean?
Everyone who got 2-3 legs now has a very high chance to get another leg really fast.