Same exact problem. Two of us sitting on the same couch (playing on seperate 360s) spent 20 minutes trying to join a match together and were never able to. This is unacceptable. I had been hyping the game at work trying to convince peopel to get it so we could all play together like Battlefield but now I feel like an idiot since there is no party system in place. Such a huge dissapointment.
The most confusing part is they all ready have a squad staging system in place with the co-op portion of the game. My hope is they can use that infrastructure to make a quick patch that allows a squad based system like in Battlefield. Without it I really can't recommend the game to anyone.