Quote Originally Posted by sanahtlig View Post
The JP wiki says the bonus from the assist skill is 8%.

Also, every indication I've seen is that assist skills only affect the soul/kamihime that has the skill (a comment on the JP wiki affirms this). Moreover, I tested skill damage just now with Rosenkreutz vs. Mordred (no buffs or debuffs applied) under controlled conditions, and allies of Rosenkreutz did not do more skill damage.
I have checked again.
Unfornately, Rose&solomon's assist only apply to themselves.

Solomonring deals 6 times 0.85x dmg (except type disadvantage/advantage). so with 80% Ability up (through buffs, passive and assist), you almost double its damage.
Using rosenkreuz with EX solomonring is also intresting, because she can hit 11 times in one turn. Something useful for MVP stealing. If there is other SSRs whose ability can hit several times, you have high burst dmg just trough ability. Without those kamis, setting ability up eidolon (Rahab) is less useful, because you only boost your soul (if rose or solomon).

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Quote Originally Posted by sanahtlig View Post
That wiki has known inaccuracies. I would treat it as I would a user blog. My first question would be what evidence / source the wiki entry is based on.

To my knowledge, there is no reliable and comprehensive source of info for this game in English. That's partly why I spend considerable time interpreting what I see on the JP wiki for users here.
I use chinese ressources. They had collected many data and did a lot math.