I'm going to assume those are Sunday rank 4s you're failing. If so, you should just run rank 3s because you can still get ssr accessories from them.

As for your dark team not being able to handle light rank 4 accessory quest, that's rather unusual. Not sure what soul you're using but I' suggest Joan with Black Propaganda, Andromeda if you swap out Sol. You don't need the -combo rate ex skills.

I only have 67.5% assault, 10% pride, 22% defender with Jack as my main eidolon with any friend's dark eidolon on my dark team and I have no problems clearing it. Using Andromeda+Black Prop, Lu Bu, Satan, Hades and Beezlebub. That's only 35% atk down and def down, -45% atk with eidolon. Take note that I was still clearing before I got Hades, in which I had Balor, and I was using Joan of Arc+Black Prop.