I've noticed when crafting that Virtuoso doesn't seem to trigger. It is meant to not consume the optional supplement when it does, and I have been using artisans with around 20% chance to trigger virtuoso.
Obviously it is random luck so is hard to say for certain, but once I noticed it wasn't triggering I went to preview and tried over 100 crafts with a few different artisans with 20% virtuoso and still did not see any usage of the ability. Since then I have been using virtuoso artisans where I can on my alts and still have never seen a virtuoso proc. I think it might be bugged.
I was primarily using Seyrin Hartport who has a 20% chance. I wasn't using any tool with Virtuoso. And I tried it on various supplements - wintergreen balm, tinkers/makers bounty and tinkers/makers quick, and a handful of attempts with distilled philosophers bounty, none of which were saved by virtuoso. I tried a few different recipes (mostly linseed oil and feywood lumber), and I tried ordering the craft or instantly crafting it with morale, neither of which made a difference.
To reproduce, get an artisan with virtuoso and a stack of supplements. Use the artisan and the supplements and instantly craft something. Keep an eye out for the artisan ability triggering, or track the number of crafts you do and compare that to how many supplements you have left.
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