For the last two hours or so myself and a few others have been playing PVE into the hive. To be honest I think it is fair to say that the 4 of us playing were beyond frustrated when after about 20 attempts the mission proved impossible to win.
At the very least you could put an option in to somehow call for volunteers so someone else can step in when someone leaves. It seems however, this basic functionality is too much to ask for.
Alternatively the difficulty could be automatically toned down a notch after a few unsuccessful attempts the difficulty could be automatically toned down a notch, particularly when operating on less than the number of people that should be in the match.
Quite frankly the kind of experience I just had does nothing to give me a good impression of STO and quite frankly leaves a rather sour taste.