GREAT GAME!
Here's my TOP team. I've beaten every epic stage with this team alone.
3 hero : Popo, Kara, Viegraf
Team : Phantom Ghost, Succubus, Were Tiger, Mighty guardian, Valkyrie, Elf Sniper.
Don't forget that the most useful spell is Shield.
To beat the black goblin you need meteor to kill them in 1 hit.
Add some Rage + Berzerk and you become unstoppable.