At least on my game. Been trying since release date to get this damn chest piece and I can't ever get it. Every chest engram has turned to Voidfang Vestments, xur has been selling Voidfang Vestments all the time. RNG is beginning to piss me off so much.
I can't for the life of me even get one from nightfall. I get any other exotic that I don't want.
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I got mine the week before dlc release from the nightfall. By this time I had give up hope, but I think RNG works just like everything else you want in life... The things you want/need come when you least expect. Try and forget about it, the day you do, you'll get it.