If you get the Leadership book that's in the bingo hall, and equip your survivors with bats and sledgehammers, they're unlikely to die in this game. It's a huge improvement over the first game, where survivors were useless meatbags that couldn't punch their way out of a wet bag.
The only time I ever had to use the Super Survivors function was with the last two survivors. Spoiler:
The two military guys that are near the save/maintenance area by the big rocks outside were a pain in the ass to rescue normally. By that point super zombies are everywhere and they swarm them and wipe them out out seconds. My hats off to anyone that can rescue them without using the trainer.