I just had an incredible vague idea pop into my head after two days of a rather frustrating flu, so I might not be too coherent or in my right mind. Basically, I'm wondering if it would have been a slightly more balanced design for 3.X if martial characters were essentially designed as mage-killers. That is to say, martial characters are made to be able to negate magic spells which target them, for example (like in my signature) fighters being able to deflect spells with their weapons or rogue-likes being able to sneak through impenetrable magical barriers. Perhaps also making abilities like Mettle and Evasion more common, where certain types of classes just completely negate spells that target specific saves.