As far as I can tell without extensive testing:
Score is based off of damage dealt and proximity to kills. If you are near a team mate as they land a killing blow, you siphon off a portion of their points. I'm not sure on the exact distance for this.
If the devs would be so kind as to give us the exact formula, it would help us give a more precise suggestion on what to tweak. Although I don't think that will happen =(.
EDIT: Trying to figure out the kill proximity thing. It doesn't seem to work anymore unless it was taken out in one of the hotfixes. It's hard to experiment without a few people to help out.