Got through the Disabled Collector Ship mission on Insanity. If anyone else needs help with it, this would be my advice.
-Grunt and Garrus, Grunt must be loyal and have Fortification/Krogan Berserker maxed with both Krogan Vitality upgrades. Garrus should have Heavy Concussive shot, AP ammo is always useful. Try and get the most XP from sidequests and as many upgrades as you can before.
-On the floating platforms, try to focus on the scions unless they're out of their attack range. So the first scion you should definitely kill first while the second one can wait a while. Keep your allies alive, they're useful distractions for Harbinger and the rest. If you have combat drones or something else to distract them, use it constantly.
-For the Praetorian boss fight, either nuke him ASAP if you have the Cain, or shoot the minions (husks, drones) first so they stop respawing. After that, dodging the praeotrian laser should be easy, just stay far away from him or he'll insta-kill you.
-Ignore the husk rush completely.
Still, damn tough mission.