shhhhh, let the crossbow be super freaking busted, i like it.(splintering bullets, all reload upgrades, tome of power, fusilade combo = become an invincible all powerful god)
you need to rush the whole pyro mage tree asap for the flamethrower build, with splinter and rubber bullets being focused next, and flamethrower scarlett can clear end wave without moving her mouse (aka a fraction of what crossbow can do)