Ancient Mixed Golems defense buff?

For some reason when these guys buff up, I do more damage to them than I can on any other monster in the game...


The 1.1m damage is on one that's not buffed; the 1.9m damage is one with the buff. This holds up over the course of me killing a few hundred more of them.


I crit for way less on stuff with very little defense (5% def vs. 98% ignore pdr)

I thought the Att UP buff removed their PDR. Even those Shrooms have a PDR of 5. With the golem having a PDR of 0, you would do more damage to it than the shroom.