does it have a high proc rate? or are we talking thala eva- levels of sh*t?
The version I had to do the final trial with, with Defense Down +5 (whatever the hell +5 is meant to mean), went off really frequently, though the effect's got to wear off before you can put it on again. I've not done any sort of testing at all with the "+10" version, though a friend who has the same thing on his scythe reckons it's about 40%*, but looks to be less 'cos of the needs-to-wear-off criterion and hitting the mob while it's debuffed.
I can't use a parser on this crappy laptop (because if I try to use windower the game becomes literally unplayable) but as soon as I get to go home I'll run some sort of test if I can't get a friend to do it for me...
...wait, KParser picks up additional effects, right? If not, I can do it out here anyway, just counting by hand. *I can't tell how he got that, though, it might be eyeballed based on reports of fully upgraded OAT weapons.