My score formula for vehicular combat games

Damage dealt will be the most important factor. Than come the kills and the assist.

35 damage on 100 total armour vehicle give 35 points.
A kill give 20 points.
An assist 12 points. (You need to have damage the target 15 sec before died.)

Pretty simple formula that will give the elite the opportunity to have good score. And also the score will reflect the real thing. It will also give credit to team players that way.