Now, how I managed to do this was simply by completing the original quest line for Elemental which allowed you access to further traits but was added in to the game by default at a later patch, the quest is still in the game and is a pre-requisite for starting the mage tower hidden artifact appearance quest line.
The quest line I personally completed was the Elemental Shaman questline, for further information on all of the quests that reset your netherlight crucible check out the wowhead guide that was made for 7.2 (Broken Shore Artifact Questline - Guides - Wowhead).
I know this isn't helpful to a lot of people as all mains will have their hidden artifact appearance but it may be useful if you messed up an alts or even an off specs netherlight crucible.
I posted this on reddit, but as a lurker on here I thought I would share this with everyone here as well.
Active as of this morning.