For farming, Nitocris (AOE Caster with 100% gauge at 2nd skill level 8) and Astolfo (AOE Rider 50% gauge charge at 3rd skill level 10).
Parvati as long as she is 10/10/10 can farm with ONE Skadi in very specific setups. Plus you have no AOE Lancer, and you have Atalanta and Zerckalot, Parvati complete te trinity of 4* who are godly with her (the rest normally needs MLB Kaleidoscope).
Zerckalot actually needs either a Waver OR specific Mistic Codes to farm with double Skadi (the fragment of 2004 one, with NP gain skill).
I would not recomend Helena for you, as Merlin sorta does her job…
ps: Dont forget to do KNK event this year to get Shiki, a excellent Arts Assassin. Last chance to do so.
ps2: In case you havent, max level and 10/10/10 Hans and Mashu. Max level Arash and Georgius as well.