[Wiglaf]

Wizards use their will to battle, lousy for a movie. Imagine two old men staring at each other thinking real hard. Ooooh! What cinematic excitement. Plus Maiar like wizards are subject to the will of the Valar, unless like Sauron and the Balrogs, they are Maiar in rebellion. However, the Valar who rule Middle Earth from over the sea are subject to the will of Iluvatar, the Creator. Even the work of the rebel Melkor/Morgoth, Sauron's former boss and a Valar, could be turned to Iluvatar's will. Each higher rank seems to be more atune to Iluvatar's will. Therefore Gandalf could have had an inkling that he was not destined to be the Witchking's ultimate defeat. As for magic, if your primary magical power is force of will and you are sworn not to exert your will by force over the people of Middle Earth and are for the time being limited to human form, you are severely restricted in your magic practicing ability.