You don't have to make magic users be as weak as a Fighter - instead make the Fighter as strong as Magic Users.
Go at look at some of the fighters of lore and mythology - Cu Cuhlainn, Hercules etc and so on. What they do is not mundane. Why can't that be the archetype for Fighters?
Fighters should also be getting built in Spell Resistance of some type. Its the type of thing they do in legends and stories - shrug off the evil spell caster's spells and keep on going.