You'd be surprised.
I've done some Haukke runs on some alternate classes and I've grouped with some rather atrocious tanks. They use Flash once and think that's going to keep hate off of the CNJ and the SMN using Bane to spread around DoTs. I've had to bust out Titan at times just to ensure that something was picking up the other adds that the tank didn't care to deal with.
I don't think this is a case of there being bots really. Many people that play dungeons are anti-social and won't even say hello at the start. I can understand the pacing of dungeons making it difficult to chat. As far as releasing, if you're close enough to the entrance it makes sense as you don't get the weakened debuff and you can just keep going. Going straight to the keys, no big deal, maybe they've ran it enough times to know where exactly everything is. (but apparently after x amount of runs they still haven't figured out how to tank...)
