I heard horror stories from players engaging mobs/boss then teleporting out of the dungeon. I always thought that was an urban myth until I experienced it the other day.
I was on my warlock running Heroic Halls of Reflection, the tank engaged the boss then teleported out of the dungeon. He watched the group die, laugh at us and left the group.
I just don’t get why people do that. Is it an ego trip? I am not sure but Blizzard needs to prevent this abuse.
Perhaps Blizzard should prevent anyone from teleporting out of the instance if one of the group members are in combat.
I am somewhat surprised that Blizzard did not put some restriction in teleporting in and out of the instance.