How Does Defense Sp / Class Base Defense Play A Role In Pvp?

Defense Skill Points acts weirdly in PvP in that damage taken is not as expected as it may seem?

In the provided video evidence, BabyEatsYou is using a Polar Star that deals a consistent 107-107 thunder damage. Factoring in its IDs and requirements, each melee hit deals 163 damage and 270 with a critical hit. I have 55.3% damage reduction through my defense SP and no other elemental defenses. This would mean I should take 90.1 damage and 149.3 with a critical hit. Or so I thought.

Checking in at moto's damage calculation thread, I'm guessing the formula for the damage to me would be:

(Base Damage) x (1+(ID Boost)+(Class Defense?)-(Defense)) - ((Elemental Defense) x (1+(Elemental Defense %))
(107) x (1+(0.429(dex sp)+0.1(melee %)+0.4(archer base def)-(0.553)) - 0 = 147 damage.
(107) x (2+(0.429(dex sp)+0.1(melee %)+0.4(archer base def)-(0.553)) - 0 = 254 critical damage.

However, in the video, I take 123 damage and 230 with a critical hit.



Am I calculating something wrong here? Or is this an actual bug?

 

I've heard something about defense (skillpoint) being wack in pvp, yeah :/