| Hux |
There are many keys to making games, learned from ancient games like go and chess to modern games like World of Warcraft. There must be balance in the system. Each person needs to feel his character is special and offers something unique in comparison to everyone else and yet for the game to survive for any period of time there must be forged a balance of power between all involved.
Everyone wants to feel like the adventure is there's and theirs alone, (particularly in a sandbox MMO) and yet still needs to be able to fill a role in a larger picture of events that unfold within the world.
Whatever choices you make in design remember this paradox of game design while still allowing the players to have the freedom of choice, without this the game quickly becomes stale.