I'll be a support class so I'll measure my success by games won over games lost.
I feel like my team would care more about how well I perform for the team over personal k/d but some people like it.
This reminds me very much of my third and fourth games of War for Cybertron after finishing building my Medic.
I joined a Team Deathmatch game, with 5 minutes left on the clock. It was first to 40 kills, with a 10 minute timer. When I joined, the score was 7 kills to my team, and 32 to the enemies. Basically, the team I joined had NO coordination, and we were up against a skilled, organised group.
At the end of the match, I went 0 kills to 5 deaths, and the lowest XP of any other player was still more than 10 times what I had. But I was quite satisfied that I had done a great job. It took them 4 minutes to make 8 kills, after getting over 30 in the first 5. Final scores: 40 vs. 36.
As the end-game screen popped up, and I could now hear the opponents (all but one on headset). One of them said "Look at that Oblivion guy's score - no kills and 5 deaths. Poor guy! *next round starts* Oh *#&$, he's on our team. Hope he doesn't hold us back too much...
5 minutes later, victory. 40 kills vs 8. I had 2 kills this time, and only 5 deaths again. I got thanked for a timely heal at least twice by every member of the team over the course of the match, and had a chorus of thanks in the endgame lobby, and a couple of messages saying I was the best healer any of them had seen in the game.
---
For Brink, my personal measure of success will be based on me setting my own personal goals - whether they be a certain amount of XP earned per match, a certain win/loss ratio, or something completely different, I don't yet know. But I'll be setting my own goals for the game, and THOSE will be what I care about. That's just what I do.