My lowest KD is my Titan, then Warlock, then my Hunter has the highest. Could be because my first time playing was as a Titan so it took awhile to build my KD back up. My least played character is my Hunter, but I mainly only use it for PvP. Seems like I do best with it. I'm sure it all depends on the player. People do better with some classes than others. Just find the class you do better on overall.