I have all my characters harvest all the time but out of 6 characters only two I can depend on to bring homr rares as if there were no other.
I have tested different theorys but the one I am favoring is this:
If you harvest at T3 concentrate on T2 and harvest like nuts in a T2 zone and rares are abundant. Yet, it wont happen over night, but after a while almost everything you hit will produce a rare.
Example: Took out my T3 to harvest in T2. First 30 minutes nothing, suddenly every rock she hit, every root she gathered from produced some sort of rare. After 3 hours she had gotten 8 coral, 5 silver and 5 blackened iron, sisal root too.
Now its just a theory, and I am still working on it, But I have a T4 that can get a rare in T2 every hit no matter what and in T3 shes about 1 out of every three shes pops a rare.
I'm working on the next tier and will keep you all updated as to how things are working out.
Tools seem to just make the process faster not produce rares. I have three that use and three that dont and no difference other than time.
Best of Luck to all,
Ny