A full illusion/skeleton summoning crew are the key to the harder difficulties. Illusions also do damage! Ignore the stupidity of some of the export characters descriptions to build the perfect team. It looks like you unlock more abilities for your edited character as well. Also it is better to sometimes let some characters die and revive them if you are about to win a battle with everyone having 1 hp.
Even my summon units suffer from a health penalty meant for the enemy? Come on, this make the useful Nerdook into a mistake when it is applied. Fix yo self.
What do you look for in a girl? What do you look for in a guy? What do you look for in a girl? What do you look for in a guy? What do you look for in a game? OH YAY SHOOTINGS TIME AGAIN!
 "Dungeons of Kong"){kind=icon}
 "Berzerk Ball 2"){kind=icon}
 "Symbiosis"){kind=icon}
 "The Lost Souls"){kind=icon}
 "Rocket Santa 2"){kind=icon}
 "The Unexpected Bug"){kind=icon}
 "Effing Worms - Xmas"){kind=icon}
 "Legend of Pandora"){kind=icon}
 "Death vs Monstars 2"){kind=icon}
 "Llama in your Face"){kind=icon}
 "RPG Shooter: Starwish"){kind=icon}
 "Insectonator: Zombie mode"){kind=icon}
 "Death Worm"){kind=icon}
 "Soviet Rocket Giraffe Go Go Go!"){kind=icon}
 "GemCraft Labyrinth"){kind=icon}
 "Protector IV.V"){kind=icon}
 "Roadkill Revenge"){kind=icon}