[Damien_Azreal]

The only boss that was actually challenging was the Octaking.
Killing him on Insane took a bit of effort. The Battlelord wasn't bad... basically after you've knocked off about half his health, just lure him all the way back to the very start of the dam.

This puts you right next to a pile of explosives.
You can pop out and unload the RPG on him, also... pick up the Enforcer's gun. As it's explosive multi-shot rounds hurt him.
Then just throw out pipe bombs to kick his health down. And being right there, you can grab more pipe bombs all you want.