I’ve also had this issue. Roughly farmed 4 hours of herbs in the last 24 hours that previously dropped Frilled Lichen while I had Bountiful Harvest 3/5. Did not get any drops. Also spent the 10g for testing purposes and unlearned the legacy talents. After about half an hour, I still have zero Frilled Lichen drops. Funny thing is that Rosecaps aren’t affected by this bug even though they are supposed to be a rare drop as well.
TLDR; don’t unlearn your legacy talents as it won’t solve the issue and you’ll be out a lot of gold