Curious why it isn't unlocked already but also when will it unlock? Not sure I see valid reason for it not to have been unlocked an expansion or two ago.
Never mind, just woke up posting is bad, listed as Gates of Discord, it starts at level 55 and when you google it showed Luclin buyable first 3 ranks, guess I confused myself.
Depends on class, most got it with Luclin, some like Druid off the top of my head, had to wait until Gates.