valour is getting double your team's average score.
See, now I am rather sure that this isn't the case. I think the other team's scores factor in.
Look at this scoreboard. Now I was too late with the screenshot, so the teams have already been switched up. Wolves_Larvae was on the attacking team and so was STR_Nokeyboard. I was topping the defending team with 96 points, of which I am pretty sure that it was twice my team's average, the second guy was on 74 points.
Yet the two people on the attacking team with a score of 108 and 118 only got valour, not me. That is why I think the other team's scores do factor in. I'll try to provide some evidence with the screenshot taken before the balancing. It happens all the time that some high scores on the other team prevent you from getting valour when you have a relatively high score as well.
Which is what I think is a problem. Your chance of valour should only depend on what your teammates do, because they fight in comparable circumstances. Especially those uneven rape rounds are where valour is a god send, but that is precisely the rounds that you have no chance to get valour because the other team had easier scoring circumstances.