It has been reported as no longer working as far back as March of this year.
My Shaman is using Fury of the Stonemother for both of her weapons but she has been using that transmog for a long while now. So it seems that if you already had it done before it changed, then it will still hold the mog.
link: https://worldofwarcraft.com/en-us/character/us/bloodscalp/tsaki
SCREENSHOT
