This is not Quake. There is no objective criterion for how good you are at PK.
Numbers don't do it because not everyone is willing to sacrifice their fun (or the integrity of a character) for a scoreboard entry. There's also a question of circumstance -- I've had one character who had an abnormal (for me) amount of PK wins owing to a string of circumstances (a certain war, a prevalence of inferior matchups in an enemy cabal, and a novelty trick that worked unexpectedly crazy well -- and got nerfed afterwards).
And a lot of 150-PK dudes are like 150/80. That's not elite.