In the BETA version of Legion, the Left and Right Bindings of the Windlord were dropped by Dargrul in Neltharion's Lair and Ashgolm in Vault of the Wardens. There was also a quest where the player would bring the Bindings to Thrymjarin in Stormheim and she would trigger the next part (which is probably the meeting with Thunderaan).

Previously we ruled this out and believed they changed it, since it was a random drop from Dargrul/Ashgolm with no prerequisites.

My mind was changed on ruling it out when Kosumoth was found in retail. In BETA, Kosumoth was summoned but it didn't require the Dark Orb puzzle that it did in retail. This implies that the devs left out major puzzles that gated players from finding content that they needed to test.

By this logic, we can assume that Dargrul/Ashgolm still drop the Bindings, but only after a prerequisite (this being a puzzle of some sort, or possibly just a hidden NPC or object to start a quest).

This puts Dargrul, Ashgolm, and Thrymjarin back on the table in the same order as in BETA, and leaving us to find the trigger that allows the Bindings to drop in Neltharion's Lair and Vault of the Wardens.

We can only assume that it will be a single step from Trigger > Bindings, but keep in mind that there could be a prerequisite to THAT step as well since we really have no concrete evidence.

Because of this, I suggest we try and find any sort of trigger in Highmountain which is where all of Dargrul's story takes place. Ashgolm's only connection to anything is that he's one of Ragnaros' lieutenants, but as far as we know he has no allies or enemies that are notable on the Broken Isles. Since Dargrul's gang takes up much of Highmountain, we have a lot to work with, and personally I believe this is the best lead that we've got so far.