Well, if you want orichalcum to be rare in your games, you are more than welcome to do so.

But your complaint doesn't really work unless you assume that every saga has the same expectations on magical material rarity.

Orichalcum, like all the magical materials, has associations that allow you to make specific artifacts that express its unique properties. Saying it needs a specical buff just because solars need to use it isnt nessicary. They'll make and obtain artifacts made of it if they need its themes- and thats fine.

Its associated with them because...