I don't like your idea because winner gets a multi anyway
But I think a change in valour is needed.
Valour is just based on the time someone survives not on what he has done.
If possible make valour be based on dmg done (just as the score is), regardless which time someone dies.
Currently people who are fighting many and maybe take out 3-4 of them and hurt a couple of others will never get valour they weren't the last guys on their team. But others who just hide all the time and sometimes do even no damage often get valour for nothing -.-