No one. I got everyone's loyalty,and I carefuly placed my squaddies in the appropriate roles.
Tali was my Tech. It was an obvious choice,because she's the one keeping the Normandy flying.
Garrus was the leader of both distraction teams. Why? Because he led a vigilante squad in Omega. And survived. For an extended period of time. His squaddies only died because of some backstabber (and who can argue against money?).
Jack was my Biotic,because,quite frankly,her abilities,as depicted in the cinematics,anyway,are INSANE. It was the natural choice.
I had Mordin lead the crew back to the Normandy,as he wasn't very good in combat (I found). That was more luck than anything else.
For the fight,I brought Tali and Jack. Tali was there for the drone,primarily. Jack was there to toss the enemies around,and provide Warp Ammo.
That is how I survived the suicide mission. Whoever said that survival was not guaranteed OBVIOUSLY didn't do enough research into Commander Shepard.