Regardless, if you want to farm with a team of three then you go into the playlist with a team of three. You can't expect that every person is going to want to take the time out of their enjoyment because you were ill prepared. If it's so important then wait or ask nicely to farm. I've farmed a place with a random after offering them a spot on our team, but because I'm not an entitled ninny did not expect a yes or no, nor did I expect him to leave if he said no.