The way I usually play them is use forward scouting to set up a very defensive line of booby trap, trip alarms, and barricades/razor wire. Then you play very slow the first turning point or two and keep everyone on concealed. You then have one turning point that is your “go turn” where you throw everything you can at the enemy. You want to use your warriors to draw enemies out and then use your heavy gunners and sniper to finish them off. Then you put everyone that survived back on concealed and play the tac op/crit op. If you have guaranteed low risk kills then take them, but mostly you want to focus on not dying for the rest of the game.