Just max wizards after you max the general buffs (except speed) and get chain lightning wizards asap.. spice it up here and there with some warriors - and you'll run through all the levels with a breeze
Just focus on the first Magic Energy Hero.. focus on her trainees dmg, and your set for almost all the levels.. only worry for absorb energy levels - but for those, prepare a fire magic hero with a dmg focus..
 "Zombo Buster"){kind=icon}
 "Incursion"){kind=icon}
 "Protector IV"){kind=icon}