Mind you, it’s been a long time now but I feel like you basically just needed to loremaster the zone and eventually a breadcrumb quest would appear to go talk to the people inside. The only thing I could find on wowhead said you need like 84/115 of all the quests done in the zone.
However, since you are wanting to do this on a hunter for the tames, I would recommend just pounding out the whole zone. I remember there were a few spirit beasts out there (in the actual Hyjal zone) you couldn’t tame unless you had unlocked certain phases of it where they spawned. Shouldn’t take too long at max level, though.