here is how to get back to the isle after choosing faction.
1. get to the quest where you have to choose faction.
2. make a macro with /reload.
3. choose your faction. spam the macro, so you get the reload screen right after clicking on the horde oder alliance button.
4. spam it while you are in the reload screen, so you get 3-4 loading screens.
5. now you are still at the isle, but cant move. relog.
6. you can move now. important: there is a timer of 1 minute, after it you will get teleported to stormwind/orgrimmar. you can reset the timer with relogging.
7. get your hearthstone at the isle innkeeper.
8. using your hearthstone doesnt work. join random/specific dungeon. write in chat that you have to go. logout while in dungeon group.
9. wait for them to kick you.
10. login. you should now spawn at your hearthstones location (the isle). if not, try again.
-> the teleport to the isle is protected. when you queue for a battleground when you are on the isle, you can /afk without getting teleported out of the bg.
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same goes for random dungeons. if you are kicked, the 5 second timer appears. no teleport. the group will get another member, but he cant join. for him, it says "dungeon is full".