I think the intended version is that they always scale with you. But things get a little wonky when you're not in a group is my guess. I have ran Stockades like 4 times back to back changing nothing, and suddenly it scales the mobs up on the 5th attempt with no rhyme or reason. I feel your pain on this and hope they implement a fix of sorts, or come out with the Heroic mode thats been in the works for a long while now of even old school dungeons.