[Exxy]

I think it should only reduce Phys DR granted by Defense, to avoid this being even more of a free damage stack.

But I also think it should treat the enemy as being Guard Broken, therefore negating their Parry skills for the duration.

I would imagine Guard Break would be somewhat redundant, considering Stalemate is tied into Defence (and betting it's affected by it). Although the argument could still be out for Eviter I suppose, but it doesn't negate the entire damage instance and is tied into another Skill (Protection from Arrows) depending on which method of attack the Arbalest is currently using.