Team Composition Question

With that setup, Ororun seems like a better fit since you can aim for shocks and buffs. While Iansha excels at attack buffs, considering the synergy with your current members, Ororun would be more stable. However, Durin shouldn't be playable... perhaps you misread it, Hou?

Personally, I'd go with Raiden Shogun! Her Elemental Burst is excellent, and since the enemies move around a lot, it seems pretty manageable to maintain buffs.

If it's an answer to your question, Orlune is better, but Dulin doesn't go well with Columbina, so if you have it, it's better to put in Sucrose. Your firepower will increase and it will be better!