It's fine if your world is designed this way, but in that case you shouldn't be allowed to play as a fighter. Do it like Magicka, say, and offer your players their choice of wizards.
On the other hand, there are things warriors can do that mages cannot. For example, in many fantasy texts, wizards are social outcasts and warriors are anywhere between accepted (but maybe not highly regarded) members of society all the way through respected members of the court. A warrior and a wizard might not make sense going head to head in combat, but they occupy different places in the social structure.