I think that ranks should be reset every week, but there should be some kind of log in place for Best Weekly, Best Monthly, and Best All Time scores.

Dual Berettas, Desert Eagle, or Glock?

You should give the mage an escape mechanism, like teleport instead of rolling forward. That way, the mage can move through walls every so often to run away or chase somebody.

Also, if he will not have a shield, some other sort of defense should exist for him, just make it harder to use than simply bringing the shield up to cover you.