After several hours of tinkering and researching, I not only disabled the cel-shading/cartoon outline graphics, but also toned down the particle generation to a level where I can actually run the game on Medium PhysX and it stays at 20-30fps. I mean jeez, my computer can run with PhysX fine ... it's just the frelling game doesn't kill inactive particles so you eventually end up with thousands of them everywhere. ._.
... Anyways, I was just practicing. I want to play UVHM but need to wait for friends, even though all our guns are going to be completely useless within 2 levels. so ... playing through on PC. Just killed Wilhelm. Whoo.