Originally Posted by Voytek
Maybe this'll help you: the 'Defend the castle' bonus game type that is going on now till Dec. 11th (I think) is an easy way to get ballista kills. You'll just be defending your keep as waves of the other team come at you. The games are shorter than quick matches and you can focus solely on ballista kills pretty much.
Yup....couldn't have say it better...you really don't need to boost it at all. It take you about 30-50 kills per special match by just doing Batista kills.