While a lot of things have DR 5/(something), not nearly as many have 10/* or 15/*. It's a diminishing-returns thing. Someone going up against that Pit Fiend (DR 15/Holy Silver) would prefer to take the +1 Sure Striking to knock it down to 10 and then use the remaining +4 for Enhancement Bonus. You'd have to change the price to +1/+2/+3 to be worthwhile.
This is a problem inherent to DR, perhaps there should only be 2 types, lesser and greater.
Sure Striking
This weapon is borderline sentient. This enhancement allows it to pierce many strange hides, regardless of the weapon's original construction, the type of weapon, or the wielder's alignment (or even the weapon's alignment)!
A sure striking weapon excels at penetrating Damage Reduction. Against DR a sure striking weapon's effective enhancement is +1 (Lesser) or +2 (Greater) better than its normal enhancement. Further it allows the wielder to ignore the first 5 (Lesser) or 15 (Greater) points of a target's Damage Reduction.
This enhancement can only penetrate DR with a listed source, for instance a barbarian's DR may not be penetrated by anything, and this weapon enhancement is not an exception.
Caster Level: 12th; Prerequisites: Greater Magic Weapon, True Strike; Market Price: +2 (Lesser), +4 (Greater).
Why am I so adamant (no pun) about not letting something like Sure-striking be available at +1 enhancement? Because it destroys the entire idea of the new DR. Now, you can say that you don't like the new DR, and thats fine, perhaps you should continue to use the old way, or invent a new system. However making an uber-enhancement for weapons that nearly negates it is not cool, imo.
Consider this agrument. The 3.5 design team restructured DR in such a way so that the only divisions would be 5/10/15, with possibly gods and epic monsters having 20. This was done to allow people to try and ignore DR, something that was foolhardy in 3e. It will reduce your effectiveness, but this does not mean it is futile. A weapon enhancement that is priced at +1 means every warrior will carry a backup weapon with that enhancement, just in case. Eventually, when he has enough money, he will buy a greater version (or what-have-you) again, just in case. The point being, once again DR will almost always be worked around, once again it will be a system that might-as-well-not-exist because of a mechanic.
I don't want that. That is why I was trying to give the mechanic more power against DR creatures, but also raising the cost. It is still possible that you will see many fighters with a backup lesser sure-striking weapon, but at that point, priced total as a +3 weapon, that is a chunk of change (and it only penetrates the first 5 points of DR). Most fighters will not consider it worth it.
However, it allows for a nice enhancement which could be said of some legendary swords. The ability to pierce
anything. Fight a Pit Fiend then a Balor then a Slaad, all the while with the same weapon. In my version a +1 Greater Sure Striking weapon is priced the same as any other +5 weapon. Against a 15 DR a +5 weapon comes up at least 10 points short per hit (assuming its +4 with one more enhancement, keen or flaming perhaps). And the +1 G.S.S. becomes a +3 weapon and penetrates all 15.
To be honest, I'm not even sure +4 is enough of a cost for such an enhancement. Which makes me even more unsettled when I see versions which are priced lower than +4.
Technik