
It's true, I have more "kills of" (23898) Bish than "kills as" (2643) ... But I started my AH career as a Bish and do still a few hops as one occasionally 
Sort of like everyone else that changes countries. You will stay where your safe and can perk points in horde and hide.
Again your graph should say one thing that is obvious, rooks horde and outnumber the opposition which leads to a higher K/D, usually having more people on game at any given time will do that.
Second, as stated by many, you will rarely ever find a rook alone without 10 wingmen at 15k.
Your graph already confirms what we know, rooks will run from a fight when any advantage is put on them. Hence, NOE's are meant to not only take what you wont die for or defend, but to thin you out, when we do that, the bbs lights up with the whines about noe's.
Everyone wants to fight, but only when your in a horde will rooks fight, cant find a fight without going to a horde. Maybe NOE's ain't so bad after all, it weakens the horde and forces you to spread it thin, if not you lose ground, and you guys with the K/D complex rarely are the ones to separate from the horde.