If youn exclusively play LA or HA and you wish to talk about cert gain you are doing something wrong already. Less than half the fight is in CQC, and in open field infantry besides medic and eng are pretty ineffective as open fields are dominated by armor and air. On top of that even less than half of those fights are symmetric encounters, meaning one force is usually overwhelming another on a point and the losing side usually have 2 choices: retreat and redeploy, or get spawn camped. In either of those scenario what class you use is irrelevant and hardly affect the outcome. If you only play LA and HA and plans to be successful with it, chances are you are choicing only zerg vs zerg close-mid range non open field fights, which severely limits your play options and cert gain, which is why you would be doing something wrong already, an which is also why K/D is irrelevant because by play LA and HA exclusively you have already restricted your cert gain potential regardless of how good you are. If you had wanted to cert gain, you would've never play LA or HA unless absolutely required (ie. base capture that cannot be assisted by armor/air and there are enough infantry resistance to warrant it's use). So your whole point on cert gain dependent on K/D is irrelevant if you plan to use LA/HA exclusively. It is like saying I, an able person, limit myself to a handicap group and see who runs fastest in it.