Clearly, having 2 laners and 1 jungler is not good at all. The two laners will have to share the gold and experience, which may be good the first 3 minutes of the game, but after 10 minutes of game the lack of gold and experience will be visible. The 2 enemy junglers can during that time harass your jungler, blocking his gain of experience and gold. And the 2 enemy junglers can help their laner by ganking the 2 laners. So, in the end, the only one of the "2 laners 1 jungler" team...