For Alliance players, when you leave the instance you come out at the Horde side instance portal. Please make it so Alliance players return to the Alliance Portal they went into or make it so that either faction can enter the dungeon through both portals. Thanks!
Having two guild groups running this instance, I’ve seen what happened. the spawn point leaving the dungeon is dependent on the group leader. If your leader is Alliance, you spawn in Boralus; if your leader is Horde, you spawn on the dock. Alliance cannot use the dock entrance and Horde cannot use the Boralus entrance, even in a mixed party walking in to the dungeon. All you can do for now is summon your party to the right continent in Tiras Garde, set your dungeon correctly to mythic, and have your members go to their correct portals.