Well, since I just run about with the buff on anyways. I did fight the Taken Colossus in "Outbound Signal" that is wearing Skyburners Annex, he did drop an Exotic Helmet. But it turned into Mask of the Third Man. I do of course have Skyburners already, and didn't have MotTM I'm more of the opinion that its absolutely random, cause I've gotten things like 9 Jade Rabbits from all over, and never seen a special or heavy engram (And have had 1-3 of just about every glove in existence).