so the highest level got most of the kills. interesting.
Its not his level, it's the sword he has equipped.
Levels gives you abilities: one game of Routine puts you to level 4 or 5, so Katari can quickly choose two good abilities (Mighty Blow and Pommel Strike), and is viable on threatening right then. But as said with a good weapon... and not being kicked from the lobby... 
A level 14 Elementalist should have every main ability, and be viable for threatening.
Level 13/15 alchemists should have main abilities unlocked, and be totally viable.
So mostly it boils down to your equipped weapon and playing.
I can probably find a pic of a level 11 Katari outscoring a level 20 Arcane Warrior, but then we are degenerating into ePeen. Most games you should be 3rd/4th on the scoreboard, just to the way scoring works (note no Keeper in screenshot), and often you'll be stood behind a pillar while the ranged players kill everything.
My point was to encourage Reaver and Katari players to keep trying the kit, don't give up from being pin cushioned game after game. Change your play style. They're both fun kits, who are different from the more static pew pew mages/bow-users, and tanks.