So you maxed out your Pistol to get the Master Marksman skill... which is ok, as Overkill on the AR and Marksman on a pistol are nearly identical.
You do not have any Shredder Ammo VII and Tungsten Ammo VII left from previous playthroughs, right? If you have, take them on organic and geth enemies respectively, as they deal the biggest amount of damage. Inferno Ammo is the best for overall purpose. Skip that Kinetic Coil and use 2 Scram Rail X. Together they increase heat absorption by a lousy 20 percent wich is countered by your Marksman skill, that should be used whenever you pull the trigger.
And your squaddies die not suffer from heat absportion, so give them both 2 scram rail X or rail extension VII along with the HE Rounds.
Wrex is good because of his Warp. On Insanity almost all organic enemies will use immunity, reducing the damage they take by 60% and it takes hours to take them down. Warp counters this.
Speaking of Warp... in ME1 all biotics can be applied on shielded enemies and and a master Lift takes a Geth Colossus out of combat, or Saren, or Soverein .... Piece a cake.
You can push or double lift them into the sky.... so they die because of the height.
All squadmates do the job, but a biotic crew lick Liara/Kaidan and Wrex is awesome.
Your team is good on a boss fight, but if you have access to Kaidan, it gets even easier, as he's got Overload, Lift, and Sabotage in his Arsenal to beat Sovereign in the final fight.
What armor do you wear? Colussus is best here (i played it with the orignal N7 armor, which is total crap on insanity.... added more spice to it). It's more a matter of damage reduction than shield power. Give them all 2 Med X Upgrades for the Cooldown, including yourself. And make sure you have the KASSA (for Colossus Armor) and Serrice Licenses so your Requisition Officer gives you access to Savant X Omni Tools and Implants. By far the best ingame.