For reference here is the ability:
harden your f lesh so that weapons that strike you are
damaged or destroyed. Anytime a melee or ranged weapon
strikes you, the weapon takes an amount of damage equal
to your oracle level. This ability does not prevent the
weapon from harming you unless the damage destroys
the weapon attacking you. You can use this ability once
per day, but the duration is 1 minute/level. You must be
at least 7th level before selecting this revelation. At 15th
level, the damage from this ability ignores up to 10 points
of hardness.
No, I don't see a glaring flaw (except for the bow destruction, since the bow doesn't 'strike' the character, but the arrow does).
It is pretty brutal, and could destroy nearly any weapon with a full attack. That might be a little broken (if you'll pardon the pun).
As for projectile weapons, arrows of a +2 enhancement (or from a +2 enhancement bow) would still damage the creature, all the way up to 20th level (since they'd have 21 hp). I don't think it's that unreasonable for an 11th level character to be immune to low enhancement arrows.
The ignoring hardness is what makes it really brutal, though, at higher levels, and makes it a threat to heavier magical weapons. The oracle is already doing a ton of damage, now it all breaks through?
A +5 longsword has a hardness of 20 and a hp value of 55. Striking a 20th level oracle, each hit deals to the weapon 10 points of damage. After six strikes, the weapon is destroyed. Yikes.
Of course, those six strikes deal 1d8+5 (weapon) +5 (we'll say STR of 20) without any other bonuses to damage, it deals 70 points of damage to the oracle on average, with five hits, and one where the weapon is destroyed (plus fighter, paladin, barbarian, magic, etc. bonuses).
There's a whole host of other issues at that level, but with average hit points, the Oracle still only has 103 hp (max at first, 5 per level after). That can really hurt. With fighter bonuses, those six strikes can kill the Oracle in two (or fewer rounds) rounds. With full weapon training (+4), specialization (greater, +4) and mastery (critical hits), he deals another 40 hp of damage, more if he uses vital strike instead of a full attack (though it would take longer).
There are simpler ways to kill something that threatens your +5 longsword, though.
At 15th level, though, it's way more of a threat (since the weapons won't be +5). It does seem a little overpowered.
*numbers and stuff*
A 20th level oracle better have a lot more than 103 hp, or it'll be a smear on the ground.
A 16th level fighter is going to have 4 base attacks on a full-attack, plus a possible 1 extra if they are hasted or using a similar effect.
Even with a moderately enchanted weapon, it just isn't going to last with RAW.
Adimitidly if you use a weapon you will strugle but grappleing her, pinning her and then tieing her up is about the best bet for any fighting class after youve done that i imagine a coup de gra could soon follow.
Yeah, the more that I think about it, the more that I think it's not so bad. It doesn't deal damage to natural weapons, unarmed attacks or any other attack.
Yes, it's darned powerful, but I'm not sure I think it's game breaking anymore.
In fact, until it beats level 10, it only will work against hafted weapons (wooden staves, maces, polearms, etc.). (since you have to be 7th level to take it).
So it's fairly useless until 11th level, at which points it becomes marginally useful, until 15th level where it becomes incredibly dangerous (but only to weapons). Huh. Sounds like a spellcaster to me.
Also, when you compare the power to spells that a caster could throw at 11th-plus level, it doesn't seem quite as powerful (especially given the 1/day limitation). I mean it is powerful, but not a huge threat.
The party may actually get mad at the oracle who uses this too much and trashes all the opponent's powerful weapons ;)
Also technically ammunition is classed as a weapon so for the purposes of the ability you could argue that as only the ammo strikes the oracle only the ammo would be subject to damage which in most cases would make her immune to missile weapons.
Nope, it doesn't make her immune to +2 or better magical projectiles. A normal, run of the mill arrow, assuming it had 1 hp and a hardness of 5 (if you count it as a hafted weapon, for the wooden shaft--I'd count it as 10 because only the steel point would matter).
Anyways, the +2 arrow has 21 hp. Even a 20th level oracle wouldn't be able to destroy it with this ability.
Normal arrows at 7th (or 11th if you give them a hardness of 10), sure, +1 missile weapons after 15th level (since 10 points of hardness is ignored), but remember that bows (and other magic ranged weapons) bestow the enchantment on the arrows, so if you have a +2 bow, then your arrows are safe.
I think temporary immunity to normal or +1 ammunition isn't that bad, especially given the relatively short duration. Heck, there's a second level spell that gives immunity to normal arrows that lasts 1 hour/lvl. (Ok, technically, DR10/magic vs. ranged attacks). A 15th level caster could be nearly immune to most non-magical ranged attacks for nearly all day, or all day, if he memorized/cast two spells. As for damaging the arrows, most arrows (or bolts, or sling stones or daggers) are destroyed or lost after an attack anyways.
At the level it becomes dangerous, everything else is dangerous too. It also makes folks break the 'hack it 'til it drops' mold, which could be good.