Kemrain said:
The way I read this, the Barbarian keeps his Dex to AC, but can still be sneak attacked, because he would have lost it. Is that dead wrong?
It's wrong in two ways, and both are questions that come up regularly because of ambiguous wording.
The first is the "even if" that's already been referenced in this thread. It's badly written, but it's been clarified by Sage, designers, etc that "struck by an invisible attacker" and "flat-footed" are the conditions UD protects against, not just
examples of some conditions UD protects against.
So if you lose the opposed check when the rogue feints, you lose your Dex bonus against his next attack despite Uncanny Dodge.
The second is the "would have lost" clause in Sneak Attack.
It refers to whether you would have lost your Dex bonus
if you had one to lose.
Let's say my Dexterity is 9. My Dexterity modifier is -1; a Dex penalty.
I have no Dex bonus to AC: A bonus is a positive modifier.
So when an invisible rogue attacks me, he says "Because I'm invisible, you lose your Dex bonus, so I can sneak attack." "Ha-ha!" I reply. "I don't
have a Dex bonus. So I didn't 'lose my Dex bonus', and you can't sneak attack!"
But the rules say I can be sneak attacked if I
would have lost my Dex bonus. If I had a Dex bonus, I would have lost it, so the sneak attack applies.
But now let's take another example - a barbarian with 9 Dexterity and Uncanny Dodge. The invisible rogue attacks. The barbarian has no Dex bonus to lose, but even if he
did have a Dex bonus, he
would not have lost it, because he has Uncanny Dodge. Therefore the attack is not a sneak attack.
It's not "You would have lost your Dex bonus if you didn't have Uncanny Dodge!"... it's "You would have lost your Dex bonus if you had one to lose!" that's important.
-Hyp.