"Why not? Not all DR is based on anything physical, so wouldn't make sense that someone with nearly supernatural insight would penetrate the DR better than the guy with the sword?"
Sure. I'm not necessarily saying that it definitely shouldn't be in the supplement. I'm just saying that if it is the only system in the supplement it is not going to satisfy a majority of customers.
First of all some DR is based on physical properties of a shell or carapace. Even the DR that is fundamentally supernatural might (depending on your imaginative assumptions) just be an enhancement to physical properties. And, not to put too fine a point on it, Wisdom or Charisma does not necessarily provide supernatural insight for a non-spellcasting class.
Another route to go would be to use Spot or Knowledge (Monster), depending on your preferences, to overcome DR. A Knowledge (Monster) check would allow the individual character to know where the weak points are in the protection, or the method for overcoming that protection. A spot check would be more immediate. You would roll each round to determine if you see the weak point in time to aim for it. Each of these options is based on different conceptions of what DR is.
Not only are you trying to sell a game-mechanic you are selling in-game assumptions, and that just makes it extremely tricky.