I too am absolutely frustrated with this. As a hunter I have only special and heavy for void damage... This limit makes it incredibly hard to guarantee kills. And even if I do get a good k/d ratio, if I didn't use the right weapon, I still lose points... I have tried and tried. I get up there and then lose progress all due to better opponents or poor luck. At the moment, I seriously want to just drop the bounty and pick it back up on my titan or warlock...