Many missions or tasks should be able to be completed by a single player or (faster) with a team. Several roles or skills are used (such as unlocking doors, defeating security systems, watching for guards, cracking safes, etc.) that fulfill tasks in the mission (in order and in arbitrary order). With a team, these may be completed faster.
In opposing missions, players on the other side may reset goals if there isn’t a team to counteract the damage to the completion status.
In competitive missions, teams may have different sets of goals to accomplish (either different locations or completely different goals). Some of those goals may be exclusive or complimentary to the other team’s efforts, and some may be block the other team if they haven’t advanced past that goal.
Mission goals may be seen as acyclic directed graphs. These graphs may be linear, networked, treed or doubly treed (with many goals in the center and a single beginning and single or few end points. Success may be based on absolute completion of all goals, achievement of a particular end goal, or a percentage of goals completed. As opposed to grinding (kill ten rats, so to speak), completion of goals should use skills outside of combat.