Sounds like all you really need is someone to dispel the atk buff, which would be bad if you had randoms but being a union, you can coordinate to some degree and more so with discord or something. Not sure if you can dispel the guaranteed double attack. Aside from that, I'm not really expecting much from this, just the usual debuff and attack.

I don't have a single SSR water hime either, using the same party with Belphegor instead of Triton. Most likely going Mordred, in hopes I can solo auto battle the other easier stuff.