Needed... Ability to ditch a hopeless party.
Much to my annoyance, it seems that there's no way to quit an instance in progress if the party you get stuck with ends up being totally hopeless. It's one thing to have no communication, it's one thing to have people completely ignore common sense and run head first into the boss room time and again, locking the party out or pulling everything onto them every time... Despite the numerous deaths of this person from doing exactly that.
A single character should not have to carry the whole darn instance or waste a whole hour and a half of their time if they get stuck with utter morons. Unfortunately, logging out for several minutes doesn't seem to make you drop group reliably. Nor can you vote to kick people out of early instances.