It is proper Netiquette to cooperate in team games. Do cooperate with the team.
Cooperation Netiquette Video Games
Cooperation means that you play as a team. It requires that team goals are accomplished. This may include helping team members accomplish goals ahead of yourself. It does not require you to play to your detriment.
Video Games Cooperation
Cooperating with your team in role play and other video games builds team work skills that translate into reality. Working together to win a video game is like working together to do anything else.
Cooperate with your team because it makes you a better player and person.