In 2 vs 2 there are two game modes: Capture the Intel and Team Deathmatch. Selection between them is random.
In Capture the Intel, you get 3 points for each capture of the Intel object (a suitcase that spawns on the map). You still get 1 point for each kill.
In order to win in the Team Deathmatch mode, you need to make more kills than the opposing team.