This is something that is bugging me for a while. I usually play with a friend online over psn and leave a slot or two open for random people. None of us ever quitted from a game or had a dc but still we both rank up our incompleted games every day because of people disconnecting on us.
Even if you spectate you get an incomplete game if one of the two fighting disconnects.
I wish the game would recognize who disconnects :/