I'd say that anybody with a K/D ratio above 1.00 will, on average, contribute to his team's score more than he will the other teams, and so is good enough. Yeah there are people that think you have to be a certain level above 1.00, but I disagree. For every kill, there is a death. If you average out the K/D ratios of everyone in the game, it should come out to 1.00 (less actually, if you count suicides), so anything above that is better than average.