I did 3 Assaults, 2 Support, 1 Sniper. 1 Support was smoke grenade oriented, so two smokes per match, with +40 defense/larger area. Assaults wore heavy armor, combined with their bonus health perks and tactical sense +5 Defense for every enemy, it made them beasts when they broke into a room with two or more enemies. Smoke, Tactical sense and they had +50 defense--their run and gun would be saved, so even in bad positions (Enemy was far up on a ledge or something) they could get right next to the them and double tap them (With near perfect accuracy, thanks to how close they were.) Since there were three of them that could do this, and since assaults do ridiculous damage close up, usually at least 1-2 aliens would be dropped. If there were more, a smoke grenade got thrown and they ones that were left didn't hit shit.
The only problem were Chrys but assaults get a free reaction shot whenever something closes to within 4 squares and I usually had the sniper and a support (Healing one) on overwatch just for that reason. Combo was ridiculously effective, and very, very safe because it left a lot of room for huge fuck ups thanks to the tank nature of the most of the squad.