I don't usually have bad dungeon runs, and usually if there's a problem it can be fixed with chatting.

I quit guildhests all the time though. They have one mechanic. The game tells it to you. I repeat it to you before we engage. If you're attacking purple bubbles, letting the orange-robed healers make the thing take half an hour, or killing gargoyles by using AoE or DoT incorrectly, then I just don't have the time.