First Wave :
Build Everything But FireBall Towers And Holy Bulwark Shields
UPGRADE START FROM Point Number 3
2ND Wave :
FireBall Towers And Holy Bulwark Shields
Upgrade Start From Point Number 1
You can kill all 4 apps at start of boss and watch anything until Boss dies
Hint 4 : if you want play as Dps App spam mages without any upgrades before the boss wave and just stand with them and dps they will out heal the boss dmg