heres a really good hint, upgrade hell drill all the way and put divine blade on about level 2, just high enough that you can use both back to back with full rage. hell drill does 165% extra damage on the next hit and the heavens blade will smash enemies. Also combine hell drill with life steal, it can pretty much full replenish your health when both are fully upgraded. I survived against the survival boss with that one fore a really long damn time.