Ignore def doesn't stack

I'm pretty sure threaten reduces the def of the monster, so there should be no problem with that

Ok.
21% blast + 15% from set bonus: (17353-18461 range)
@ Chipmunks (10%PDR).
17353*2.89*1.495*0.936 = 70176-74656
17353*2.89*1.495*0.921 = 69051-73459
Observed range: 71234 - 75769
That's... neither. The upper indicates 49.94% (or higher) ignore PDR. The lower indicates 50.11% (or lower) ignore PDR. So it's a pretty good guess that I'm at 50% PDR. Somehow.

 Spoiler

Same 9 buffs active, using Blast 32 (says 21% to ignore def) and the Silent Crusade set (says 15% ignore pdr)

+ bonus threaten damage

 Spoiler

76897 -> 64.08% (or higher) ignore PDR.
Which, assuming Threaten just drops the mob by 30% (to 7%) and then the same 50% is applied, should be 65% ignore PDR. Rather than additive (to 80%).


edit: switched to a different set bonus (2% atk 2 matk) and still get exactly 50% ignore PDR with blast. -_-