Accoding to a hotfix list posted for December the 19th, this item was supposed to be unbound and available for trading / mailing and posting on AH.
It’s December the 23rd, and the one I have is still soulbound.
Another person from my guild have the same issue with Formula: Illusion: Primal Frost - his is also soulbound.
Here’s screenshot created today:
This makes me think that not all of those hotfixes have been implemented, seeing as the design I was hunting all this time (Elemental Lariat) still haven’t dropped for me, despite killing all elite rare spawns once a day on multiple characters ever since Primal Storms started. Even after the hotfix that was supposed to be implemented by now.