From what little I have been able to find on this augment after doing a LOT of research, it appears that this augment drops from one of the "dusty barrels", "chests" etc that are randomly placed thru-out LDoN dungeons.
I have not been able to find out if it only drops from these in Raid Instances, or if possibly it drops in the "hard" group missions also.
There is next to no info available on this drop and this is all I've found to date on it.