I bet there’s something akin to a tier list among the Japanese circles but I don’t know really. I think a better question might be what particular skills are to look out for. Imo Skills that give two passive bonuses like Fervor and Concentration are quite strong, anything that charges CP especially as group buffs. I’ve personally found buff that just flat out increase defense strong too. Debuff wise I think Frozen is absolutely ridiculous, which makes Chernobog obviously quite powerful imo especially when coupled with characters who have skills that increase skill chance.
I can say it seems almost unanimously agreed on that Jinn, if you get him, has one of the best skill kits in the game all round. It’s really hard for me to say other than that though it’s very situational and based on team comp and of course husbando factor.
Though I do think units with really good kits could be a good topic of discussion.