Any ideas?

[Angel Daggerfury]

^^
Either this trick or get on the house next to Darkhart. I only use the bottom of the ramp if theres like tons of people who won't fit on the house grenading him. At the bottom of the ramp, the only things you can do is throw nades & daggers & shoot bullets. Coz if you grenade him from the side (not the roof) on the house on the left in the picture, Darkhart will be close enough so you can Throw Dirt for Dagger & Taunt for Cutlass in addition to the stuff mentioned before, so you could work on your lvling for nades, daggers, gun & cutlass.