Zagara bug is not fixed and here’s why it looks fixed:
The first game you play, it will be fixed. HOWEVER, after that game is over it will de-allocate all your mastery and revert to the old behavior. You will have to restart the game, and then reset your masteries, if you want to play with the new mastery set.
So as of right now, it’s actually possible to play with the old mastery choices or the new ones for Zagara.