So, I was at work and it kinda dawned on me, what if they're being used for the Class Accessories?
http://us.battle.net/wow/en/blog/141...ries-5-20-2014
It looks like there are certain levels to classes accessories. Maybe the highest or best level of the accessory is from Mythic only and is a legendary drop? I know this idea is extremely far-fetched but I would find it pretty interesting assuming the accessories are extremely well made/awesome kinda thing if it requires a legendary for their final stage.