Noticed this by chance. I don't know how useful this can be, so if it's completely useless mods should remove this.
You can't do this if you have already completed The Assault on Zeb'tula (Horde) or The Assault on Shaol'mara (Alliance). They are a part of the intro quests to the Isle of Thunder.
Start off by going to Shado-Pan Garrison in Townlong Steppes (map) and pick up The Storm Gathers (Horde / Alliance) from Scout Captain Elsia / Vereesa Windrunner respectively, proceed with the quest to arrive at the Isle of Thunder.
After landing on the boat deliver the quest and pick up The Assault on Zeb'tula / The Assault on Shaol'mara from the same npc (do not complete the quest). That's it for setting things up.
Now whenever you are in a dungeon or raid, you can abandon the quest and walk out the entrance to be ported to the same boat you picked the quest up at. From here you can either use the orb to teleport to the Isle of Thunder or the portal to get to Townlong Steppes. Remember to pick the quest up again before leaving the boat.
edit: You can also visit someone else's garrison and then leave group, when you get kicked out you will be ported to the same boat mentioned above making this a little more useful in my opinion!
One use I can think of is if you need to kill Nalak for the mount you can enter the nearest dung/raid or a friends garrison to get to the Isle of Thunder.
I haven't tested if this could work for introquests to other zones like IoT, so if you get this to work elsewhere post below.
As a disclaimer I haven't really tested this for the alliance quests since I only have one character on my new account, so if this doesn't work for alliance please post below.