Beat CoT5 before starting my second playthrough. Had Goblin Soldier, Fire Succubus, Magic Cannon, Taurus Warrior, Dragon Rider and Dwarf Engineer for monsters with Comet Shoot, Phoenix Strike and Hercule's Strength as skills and hero Viegraff the Red. Too bad that's not good enough to beat any of the other caves.
The high numbers do make it more difficult, but you can do it!