No you don't. I think it is more important that you pick the right people for the right jobs.
Tell me if anyone did anything different and their results.
I picked Garrus to lead the other team both times. Picked Samara to create my biotic field. Picked Legion to crawl through ducts. Picked Zaeed to take survivors back to ship. Also had loyalty of everyone. I didn't fully upgrade anything. I had a few of the characters upgraded, but not all. Only upgrades to ship were fuel capacity, improved scanning, the cannon, the shield, and the armor. I didn't increase probes, upgrade clinic, or anything else.
Maybe it is a matter of luck though.
I followed what others did to get everyone out alive.
Used Legion for the tech role. Used Jacob as Team 2 Lead both times. Used Samara for the biotic shield. Had most of the upgrades, but not all for weapons/armor/tech. Ship fully upgraded. If I used Tali for the escort, she made it back alive but Mordin died. If I used Modin for the escort, Tali died. All team members were loyal. Can't see why I kept losing one. I even set the difficulty to Casual to shorten how long the fights lasted.
There should flat out be a basis for why a teammate makes it or not. If it's luck, getting them all out alive will be very frustrating.