A couple of things to help with your game:
- Add in more varied attacks to help sell the idea that you're playing as the boss. Nice touch on having a cooldown on the shockwave one, though.
- Have the shockwave kill the heroes rather than just pushing them away. Add up the points based on how many you kill.
- Add in an unconventional enemy that would help invalidate the player's safety by just standing still and therefore, cheesing your game.