One of my favorite things to do in an online game is to track my ranking of a meaningless stat that is highly correlated to how long I have played. (This is not sarcastic)

Currently the achievement point total feels arbitrary as we have no reference to what it means. On the other hand rankings provide a feeling of progression and accomplishment, It encourages players to try all the content that a game offers and extends the replayability of a game.

It would be really nice of World, Server Cluster, and Global Rankings were added. It would give players something to strive for when they reached their 'wall', as well as encourage community effort to help each other complete some of the achievements.