I've recently aquired one and noticed a pretty big decrease in DPS on Vana, even poisoned, compared to Blitz.
Could it be that it is intended to be used in conjunction with a Blitz, so once it poisons Vana the Blitz can deal massive damage?
I wish it were able to effectively solo Vana by itself though. I will do a Plague+Blitz Vana once Im home, and test if using plague till poisoned and then switching to blitz is actually effective, maybe try to beat a personal record...
What do you think about the Plague Needle, and how is it effective?
It's decent, but that's it. Poison vials + 4 Blitzes > 1 Plague + 3 Blitzes