When you get to the area where General Darkheart is standing in front of his tent, carefully stay right side and walk past the gunnery shop to the first house on stilts/ramp....walk up the ramp onto the porch and stand between the post and the porch rockers.
I lobbed a couple of grenades to get his attention, make sure he has red circle first...then switched to pistol(triple is all I got), and alternated venom and bane mostly, couple of hexs....you will have to move back and forth along length of porch(Do not fall off!) until he gets as close as he can beneath you...as I said try to end up between post and rockers and do not let up firing,,I received no damage after the initial barrage of daggers he cast while running towards my position....so cool!
