Aetherdrift Mastry pass, is NOT rewarding Mythics.
The mastery pass is supposed to give you 2 Mythic Aetherdrift card rewards for leves 9, 12, 21, 34, ans 59. It has not donee so for any of them. Every time I achieve one of the afore mentioned levels, it rewards me with some coins and experience, but never the Mythic rares. Seems like a pretty consistent bug too. There are a lot of post about it, but nothings being done to fix it. Where's the support for your customers Wizards? We've clearly paid, but are not getting what we are supposed to.

-
Rezzahan#77802 commented
And have you ever checked wether you got the cards right after reaching that level? Notifications in that regard are spotty, and have been for years. Moreover, you only get to see the new cards highlighhted the first time you enter the deck/collection menu after a game. Once you have been in some type of deckbuilding (even for a Limited event), the cards are no longer highlighted. So when you reach such a level in your mastery, check your collection right away.