Hi there,
Did a vendor reset on Benevald 60 times by now , 40 times on ultimate and 20 on elite.
Only seeing green/rare blueprints, not a single epic one so for.
Did something changed? regarding to the wiki he should sell the recipe sometimes.
Realy bad design if im forced to visit him 100+ times 
Difficulty does not matter when visiting vendors, only your level
What is the level of the char you did try with?
looks like vinelton also sells the blueprint
i was lvl 78 while trying to get the blueprint.
also tryed that once on elite 5 minutes ago ^^.
Atleast he sold 5 or 6 lvl 75+ epic and legendary blueprints.
but i only have one skeleton key left, is the chance decently high to get the recipe there? Or its like a 1 out of 100 chance?
just run around the 2nd zone for like 10s to reset his inventory
afaik you can not reset Rouge-like vendors?
by āsecond zonā do you mean 2nd zone in the entire ancient grove (Feral thicket) or the 2nd zone in the skeleton key part of the dungeon (Tainted woods)?
It used to be possible to reset Vinelton by going to the last floor of the dungeon, wait a few seconds and return to a fresh inventory. Havenāt done it in a while, not sure if it still works.
When I did that, the vendor disappear. Or at least they used to do that (also BoC and SoT vendors did disappear when entering another level in the said dungeon). I have not done this in a while either
that what I mean, it should still work I did it a few days ago
Well there are a lot of blueprints in this game. If you are dead set on grinding this specific blueprint out then it will naturally take quite a bit of time. Just like it would to farm any other specific legendary/blueprint.
Farm Bastion of Chaos on Elite. It drops lvl 75 recipes like candies.
There are other places to farm bpās like the rougelikes on Elite (the boss chests)