If I'm understanding things correctly, Demon Hunters are the only race that can xmog their weapons into the Warglaives of Azzinoth. Researching this on WoWHead, I'm a little confused and hoping someone can help.
The steps are as follows:
Step 1:
Farm BOTH 1-Hand & Off-Hand Warglaives on your Death Knight, Demon Hunter, Rogue, Monk, Warrior only.
Get this account-wide Feat of Strength achievement on 1 of these characters.
Step 2:
Run your Demon Hunter through 7.2.5's new Timewalking: Black Temple event.
This Feat of Strength plus killing Illidan Stormrage with the new Demon Hunter class at level 70 will give you the soulbound item to Transmogrify your Artifact Warglaives to the Legendary Warglaive appearance. It will likely cost a hoof and a wing to pay the fees. Good luck.
While running my Rogue through black temple, I got the off-hand Warglaives. Should I continue farming on my DK, Monk and Warrior, as well as my Demon Hunter to get the main hand? Or do I need both the main hand and off-hand warglaives on the same character, to equip them, to get the feat of strength?