The Ghostmaker's ranking system I believe is based on the ELO Chess ranking system. The better you do against better players the higher you climb. Beat someone you should beat and you don't get much credit. Lose to someone you shouldn't lose to and you drop.
If you mean the Rank on your profile, that is based on your available points and isn't terribly meaningful.
Multi-accounting gives you an edge in many ways. Allows you to sniff out what other players are really up to by hearing two sides of every tale. Allows you to sacrifice one country to benefit another, directly or indirectly. If done to gather points, having a higher amount of points allows one to be in better quality of games, with more experienced players and those who are less likely to go CD.
Funny that you should mention the World Series. In baseball if you can hit the ball 1 out of 3 times that is considered pretty good, right? On base percentage of half the time would be good right? So if a player can win or draw, against 6 other players a third to half the time, that's doing pretty dang good. And yes, the good players know the board, know peoples motivations, know what to say and how to say it to get the results they want. Not all the time, but enough of the time that they are more likely to end up on top than not.