Third boss killed on my 3rd round through using only Rifles and Riots. Never even unlocked Scouts or Blasters. Just dumped everything into resource drop boosts, mook damage, and Riot/Rifle power
Doing the same thing here, slowly whittling away at the second boss. I don't actually see any reason to end mission when I can grind at it forever. There's no end condition either for some reason.
Edit 1: I failed and had t restart. There was the big tesla coil guy after the second boss that bodied me and it ended up walking through the portal so i got no materials for upgrades. I proceeded to get bodied. RIP :(