I used to play other mmorpg before this , Knight online . There was a chat window in the bottom corner , in the PvP zone , that listed the names of ppl killing and getting killed ,
ex: Person X has defeated Person Y .
Here couse we dont know the names of the oppsing faction i think would be enought to see exp: Person X has defated invader Y . So ppl would accutaly see who is doing the kills , like u have in SPvP . This game is all about prestige so that would give the “leet owner” some prestige i think . This should show the last hit before player is in downed stage like in SPvP . You already have it done , so i dont think it would be a problem to implement it WvW.