Penetrating Strike ACF/Heavy Fortification [3.5]

[Nada Rakshasa]

I've built a rogue for an epic campaign who uses the Penetrating Strike ACF (you may deal 1/2 sneak attack dice against a flanked creature who would ordinarly be immune to sneak attacks). It seems very likely the the BBEG is going to have Heavy fortification armor (100% chance to avoid sneak attacks/critical hits).

My question: For purposes of Penetrating Strike, does heavy fortification grant a creature immunity to sneak attacks? Would a rogue with this ACF be able to deal have sneak attack dice to a creature wearing such armor?

[Hyfigh]

Per the RAW of fortification it negates the sneak attack damage done 100% of the time (for heavy fort, anyways). I could certainly see, and would allow, the argument that 100% chance to negate the damage is immunity. For that matter, the negating of the damage at all would lead to immunity. If they fail they roll SA damage rolls normally. If the chance suceeds to negate Penatrating Strike kicks in and the SA applies at the 50%.


edit: corrected my post.
edit 2: I can also see the argument that negating something is not truly immunity, as immunity is an in-game-term.

[ShneekeyTheLost]

Best way to avoid Heavy Fortification is the Mage Slayer feat chain. It's one of the very few things that practically requires Pierce Magical Protection to bypass.