K/D isn't skill at all. Just shows how good you are. Honestly someone can have 4.0 of K/D and all they've done is either:
Play flood Camp
Skill revolves around the player alone. Trust me, on Reach, my K/D is probably near the same as 4 and I've been owning 2.5 to 3 Kders. Mostly because they camp n I'm a camp killer or played too much infected.
The closet to skill I've encountered is maybe the Arena to Rank playlists