I believe Final Kills should be worth more XP then regular kills:
Final Kills are more difficult to get than regular kills. After breaking a treasure, the unlucky player that lost their treasure will be more defensive, running away from a lot of fights. Also, they bowspam the heck out of people sometimes. Final Kills should be worth 25-50 XP. I feel like this would encourage other players to attack people without treasures more, which will open some more strategies for players without treasures, and for players trying to eliminate them from the game.