Pharos Sirius is the one that gave me the most trouble getting the squadron through. That damn Zu mother mid boss is completely impossible if you're a DPS, because all of the chicks will ONLY target the PC and ignore all the NPCs, meaning you have to kill them or you'll die yourself, but the more you kill, the stronger the mother gets. So you have to selectively kill the most dangerous chicks and be able to survive the rest of the fight. It took me way more tries than I could keep track of.