Can you make the ranking value a score that is based on won battles devided by fought battles? that would make much more sense. it would show who truely is a good commander.
pvp score additionally should take into account if the fight was against a player of same level or one of lower/higher level.
digging even deeper into that idea, instead of taking into account the players levels you could base the score that is gained in a battle on the army setups in the battle. meaning that if a player is capable of winning a battle with a weak setup against an opponent with a strong setup, should give more score than winning with evenly strong setups. that would make the most sense, but might also be a bit complicated.