Here is a guide of how to finish Expedition:
Get Medusa, and Moon Legendary, and power her to max, and enchanted gear.
Same with Cyclops.
Use this 3 heroes through all the Expedition, to charge other 2 heroes.
1-1: Medusa, Cyclops, Moon, Heroe 4 and Heroe 5
1-2: Medusa, Cyclops, Moon, Heroe 6 and Heroe 7
1-3: Medusa, Cyclops, Moon, Heroe 8 and Heroe 9
2-1: Medusa, Cyclops, Moon, Heroe 10 and Heroe 11
and so on...
Use Moon White skill to energize all heroes, once per battle.
Use Medusa to freeze enemies, only when needed, use only 1 freeze per battle if needed.
In bone lines, put héroes that don't require White energy to be effective: ninja, wee, bone, witch.
Get as many héroes energized as posible, so you have enough héroes to choose from for dificult battles.
I use this method daily, and have no problem to finish Expedition.
Hope it helps.