For farming I'd only ever use her against Man Attribute Riders. Her common best case setup is very expensive, and she's a servant you'd typically like to avoid getting too much bond on so you'd normally not farm with her. Gray is a better option with the caveat of needing a 60% CE with her best setup. Optimally Partake with the King or A Walk in the Park, and Summer Valks are better if you have Black Grail, and barely worse with Ocean Flyer. Huyan Zhou is better against Riders specifically because her refund is shaky, but only really viable in 3-3-X waves. And in NA's future Tez and buffed Cleo are better. Nobody else is really worth mentioning. Assassin is definitely the worst class for farmers. For a DPS she has a few things that make her viable if you want to use her. She has the second best Arts card in the game for refund, charge loss on the NP and the CD reduction which could be used on a support instead of her, but her survivability is nonexistent so she'd heavily rely on her supports, and her NP damage in a CQ would be very low most of the time. Mine is accidentally NP2 so I'd get more use out of my personal copy.

You mean, Human Attribute enemies.

Thks for all the feedback. It was helpful, To be honest I wanted to know if Koyan is worth grailing to 120 as a viable 3-turn farmer. I reached a point in the game where I'm contemplating 120 at least 1 each of the main 7 classes,

Lancer - Melusine(Fully Foued and 120)

Saber - Arturia(Getting there and fully Foued)

Archer - Gil is a good candidate but I'm holding off for tat NP changing archer in the future

Berserker - Summer Ibuki(I got her by luck at the end of summer but I'm holding out for more copies. Fully Foued)

Caster - Didn't bother. No Caster can outdamage Chen Gong NP.

Assassin - Koyan was a candidate but now having 2nd thoughts

Rider - This class is big [?] mark for me causes no one actually sticks out for me.

If farming damage is your main consideration for 120 I would advise against anybody other than Arash and Chen Gong.

Nah, grailing to level 120 for farming is a good thing. I did that with Summer Kama.

Well, for Rider, Habetrot makes most farming Riders inert lol

But if going purely for SSRs, then yeah, it's just a matter of picking your favorites,

Agreed that Habetrot is the only option that even remotely makes sense from a farming perspective, although I still would never do it for farming alone. If your favorites happen to be great farmers, it's a nice bonus to grailing them, but to have it be the only reason is a terrible idea IMO. But everyone is free to do what they want with their Grails. I don't judge. Just to put it in perspective, the difference in damage for SSRs between lv 90 1K fous and lv 120 2K fous assuming a 2K attack CE is less than the difference between NP1 and NP2 (unupgraded).

Any difference is a good difference. I usually deal with quite tight damage (1, 1—1,3 million damage) at 90++ lotto event, so clearly grailing works for gameplay, not for character.

Well my Criteria for lv120 is extremely simple. They have to be able to function as both ST/3 Wave AoE. Morgan is probably a prime example of this but since I wanted Meluko alot more I nvr did get Morgan as a zerker so S.Ibuki took on tat role for me. In fact for any archer/zerker challenge fight I always bring my Meluko, since she is really monstrous in both roles.

The reason I was contemplating Koyan is cause as super buffer herself it would give her more space to pile on other buffs.