The number of kills you get in Control should be a function of the number of zones you capture. If you don't capture any zones (or only the one easy zone at the start) you don't get credit for ANY kills.
Or if kills only counted in fractions of score based on how many zones you currently have.
- 25 points per kill with 1 zone controlled
- 50 points per kill with 2 zones controlled
- 75 points per kill with all 3 zones controlled
with an extra +25 points added to score for
every 8 seconds you keep all 3 zones controlled
Otherwise it would only be 10 points per kill if your team has 0 Zones Controlled.