I wonder if this was because of the increased chance to find a rare. It is possible that the mobs carrying these augs could be effected by the game's increased rare mechanic. As since the change I have not heard of anyone with your type of luck, except when the increased rare mechanic was active.
Last Tuesday (May 21st) , I cleared Fire. Got 5 19s, 2 Luck. So nope, nothing to do with increased rares.
