Is there a battle ground? Or will there ever be a battle ground? Such as an arena you sign up for. If there is, then I don't mind the PK debuff. If there is a battle ground and you want to kill people outside of it - in a PvE environment - then you deserve a debuff. Plus, by what is being said, it sounds like you don't get it FOR ONE KILL, it is for multiple killings? If it is for multiple, maybe there is a timer between each kill so you are in the safe zone of not getting the buff.
Also, I noticed that you actually die if you PK someone, you die you lose exp but the person that wanted to kill you outside of a battle ground gets to live?
I kind of like that debuff revenge.
If there isn't a Battle Ground then this game isn't PvP oriented because there is no official place to PvP. So, bye PvP fanatics - game not for you.
ALSO, someone mentioned getting points per kill for a PvP tier system to get items that are SLIGHTLY better than that current lvl's gear. No. Simply no. This game has legendary items and a legendary item WILL always be top lvl gear for that lvl.