I'd recommend going solo to complete this one. It doesn't take long at all, especially in that DZ03 (slight DZ04 action) circuit. The subway right next to Torch's spawn in Bryant Park re-populates so quickly, as does Torch himself. He'll sometimes spawn as a heavy (Animal, maybe?) and that slows things down a tad.
You can also hit the first subway you come across when entering DZ01 from the bottom left checkpoint. That guy spawns quickly, as well, and is only level 30 so he burns down in no time.
Cool thanks, DZ01 is my preferred location. Way less people cuz all the Rogues seem to be trolling the mid to northern areas.