How to beat Matriarch Benezia with little health?

I had this problem when running through on Insanity. I ended up doing the following after many, many tries.

I ran away from Benezia, back toward where you come into the room. I also made sure that my squad was following me. There were some commandos there, and took them out using powers and the squads guns, and then made the left to that platform.

From there, I personally used my best long-ranged weapon and took out all enemies that could see me from there. Benezia was not one of them. Once I slowly and carefully picked off all enemies, allowing armor to regenerate between each, I then had my entire squad attack Benezia.

I also had the Unity power for all of this, but I don't think I used it at all during this battle once I figured out this tactic.

I think that the best thing you can do is try something other than take her on right away. Bide your time and take care of minions first. Use talents liberally (Shield Boost, etc.)