When you join, you have to be actively involved to count toward the stat reduction. Throw a flash or smoke, then kinda wait for the numbers of people to join. When its around 8 to 10+, then its safe to fire away.
Less than a day left till my mission expires. Finish work at 16:00 torn time today. Don't know if there'll be enough people but maybe try again tonight some time. Anyone know how long I have wait to get the mission again if it expires? Cheers.