For castrum:

Pull the search light guards, let the healer hit the search lights, wait for cutscene, then pull everything to the door.

Second section, hug the right wall, hit the search light guards, grab the magitek vanguard because he has one of the bombs you need, then make a straight shot for the pump area. Jump and provoke to grab the right magitek, someone else should get the left. You may need your invuln here. Then run to the next boss door.

Third section, pull everything until the cannons and let people blow them up with the cannons. Keep the colossus targetted so you can stun it when it tries to destroy the cannons. After the search light's gone, run right and pick up everything unitl the next set of cannons and hold it there until they're dead. Then kill boss.

Final section, drag all the enemies to the cannons. Three members run ahead to the parade grounds. One (preferably not the tank) grabs the magitek colossus to bring back to the cannos, while the other two open the door. The tank JUMPS and uses their ranged attack to grab the enemies on top of the platforms, bringing them back to the cannons again, while whoever is with them hits the search lights and then spams AA guns to bring down the airship and open the boss room.

For Praetorium: Just run lol.