[caliaca]

Yin and Yang are famously not very good with their split scaling and mediocre skill in double dao. There's already been a lot of suggestions to buff double dao (which should happen) or maybe change their scalings (which I don't think is a good idea).

Instead, I'd offer- if Yin and Yang are both equipped, the one in your main hand gains spelledge for their respective domain.

That is to say, if you are duel wielding them and have Yang in your main hand, you can now cast Mercala domain spells. If you have Yin in your main hand and are duel wielding you can now cast Huegesson domain spells.