Unless you have 9 SSRs of the element(s) you want for a given party, 2* gacha SR weapons are probably gonna be fine to keep around. For example, depending on party comp, Beel's weapon at 2* with matching preferred weapon type bonus should pull ahead of a 3* dark raid gun, while a bit behind the raid axe and lance. But the dark raid axe and lance have defender instead of assault as their skills.

My general thinking: Don't be in a rush to fodderize things that are harder to replace, like gacha SR/SSR. The stuff that should be more easily replenished (raid weapons) are probably what you should be looking at if you're at the point of needing SRs to level up skills.