I don’t like how you get extra units for getting the most kills even though it doesn’t necessary contribute to winning the game resulting in playing more for kills instead for a win (collecting orbs).
With that I suggest changing the bonus rewards at the end from “Most kills” to “Most points” and make these things give points:
Killing a player: 2 points (or 3?)
Dropping an orb in your own base: 1 point
What do you think?