MiracleOfSound said:
The following sections/enemies keep popping up, so anyone who has beaten them it would be great if you could share your tactics for them:
The Two Scions and husks on horizon
The Paetorian battle on the Collector ship
Geth Colossus
I've done all these bits on Insanity and, to be honest, I found the two Scions and the husks the hardest of all of them. I was an Infiltrator on both playthroughs (Well, I'm approaching the end on Insanity run but you get the point). Here's what I did for each one:
Horizon
I hated this battle. I had Miranda and Mordin for this. The problem mostly lays with the Husks as they just keep coming. I found running in circles around the Scions to work most of the time. After a few times dying here you'll work out where the Husks are popping up from. Try and head for the back and make sure you have some medi-gel, you'll need it. If your squad members can take some of the heat off you, you can pick the husks off little by little. Take the Scions out last, but keep running where possible or their shockwave attacks will nail you.
Collector Ship
Oddly enough, I found this easier on Insanity than Veteran. Take the Collector Particle Beam and save the ammo for this battle. I had Miranda (for Warp) and Thane for this mission. Get Miranda to warp it's biotic barrier as much as possible and just blast the Praetorian from the highest point (right by the entrance) with the Particle Beam until it dies. In my game, Thane more or less held off the incoming Collectors and Husks, but keep an eye out from time to time.
Colossus
This battle was a bastard too. I had Grunt and Samara for this mission. Take this battle one section at a time, clear one area, move. Clear the next, move. Also, take the sniper route, it's easier. More Geth will spawn as you go up the ramp, when you near the end of the crate run (cover next to the walkway wall, it'll protect you from the Geth, the Colossus and the sun) and as you hit the end of the walkway, although remember the last spawn point they will attack from behind you, so stay alert and kill them before moving on. After that, it's just a case of pummeling the Colossus until it's dead. Cover, shoot, cover, shoot. Incinerate and disruption ammo are useful here too.
Hope this helps.