So it's not a support build cause sometimes you get kills? Ok... my bad.
I understand you see a support build as something that isn't succesful in a 1 vs 1. A longspear character's purpose is stabbing people, when is a longspear character succesful? When he is stabbing people. Who is the better longspearer (support build)? The guy with 15-3 or the guy with 6-8?
Everyone's purpose in this game is dealing damage, there are no builds that do not have dealing damage as their main purpose (exception is a 13 shield build). Everyone's purpose is essentially getting kills. Some choose to hunt game changers and might get 1 kill that wins the round for them. So K/D doesn't perfectly cover someone's skill, but still it gives quite a good impression of someone's skill.
I believe I'm making perfect sense here, please tell me why if I'm not.