Beautiful looking game! I like the concept and it fits the "roles reversed" theme well! It plays very smoothly and game's task is very intuitive and clear.
Gameplay wise, it felt like deploying the enemies randomly was a pretty effective strategy, though the fireball-shooty-guy did seem especially strong. Does the hero change up his attacks in any big way ever? If the hero had phases, then players would have a reason to send a different mix of enemies depending on the phase. Currently you don't really have to think to win.
Still, great work!!!