Mechanics - Team work is key but when fast leveling and increasing power builds your characters you can kill anyone of your teammates in order to get more experience. Earlier kills gains more experience. Kills near extraction give little to no experience if entire team survives.
How would you propose to deal with the following situation:
Step 1: Start a game
Step 2: Kill your team member straight away for the xp
Step 3: Leave game
Step 4: Go to Step 1