Unfortunately, I don't think there is any good team on defense. I used to use two separate teams, and found that to be a pain because of the constant micro-management. Personally, I use the same team for both sides now consisting of black widow with her gray tactician uniform, Dr. Strange in his alternate blaster uniform, and my agent wearing the scrapper or infiltrator power armor. I find I'm able to win most battles on offense, and maybe 50% on defense.
I don't consider myself a master in MAA; so, if there is a tried and true method for defense, I haven't found it yet.