Tip for boosted or Demon Hunter characters:

[myrroddin]

If the travel system tells you to go through the red Dark Portal (text continues to say green) and you either fly or walk through and nothing happens...

Talk to Khadgar. His quest will be low level, and there is the WoD cut scene that is skippable. Now you have unlocked the new Dark Portal.

Totally forgot about accepting the quest Assault on the Dark Portal.

Hope this helps someone.

[myrroddin]

Gah, should have realized: you have to finish the initial quest line until you get a Garrison Hearthstone. I tried simply riding away to my destination, and Khadgar pulled me back.

There is at least one Legion gathering quest (Herbalism) that requires you to go to Azeroth, Northrend, and Draenor. It's that last one that is sticky business.

[ZG Support 1]

There should be a portal in the main cities (Org and SW) to take you to the first WoD zone (Frostfire Ridge and Shadowmoon Valley) without needing to do the WoD intro to get a Garrison.