bkbandit, kills and deaths are not all that are taken into account where rank is concerned. Youll also have Hit%, damage points etc etc...
Also, which rank are you talking about? Overall rank or fighter rank? good fighter scores and k/d doesnt mean you have a good overall rank as well (the one that shows on ROSTER is overall btw).
Ill take your example Blukitty:
Rank: 13 (fighter) 3353 (bomber) 63 (attack) 3453 (vehicle/boat) 1582 (overall)
Blu apparently flys only fighters (and from the number of sorties only rarely in attack mode).... the low bomber/GV rank drag the overall rank low.
For details on rank and score for each player, check up the Scores page under Community. Keep in mind that rank/score is updated once a day, so some things might not add up 100%....