I disagree with most of the people here about SS3. The whole point of a brave weapon is to double and kill the opponent before they can retaliate, and Cordy’s Atk stat certainly allows that. Why worry about quadding when you can kill in one initiation?
Here’s roughly the Cordy I’m thinking about using. Stats adjusted for Resplendent stat boost, except she should have two more HP.
The idea is to kill everything on the first initiation, charging up Galeforce every now and then. Other ideas for Specials are Moonbow, for maximum kill potential, Miracle for the occasional gimp survival, or something like Noontime for the extra healing.
Mystic Boost keeps her health topped off, and works well with her weapon’s effect. Since she should nuke things without them retaliating, she should be able to heal a lot with Mystic Boost on any given “normal” turn. Atk Smoke gives her effectively 36/39 defenses, so she’s actually really hard to kill on enemy phase. This is especially including her weapon effect, which gives her 44 speed, just the right amount to avoid most doubles. With 50 HP, and probably not getting doubled, that’s 79/82 bulk, even more if you count Atk Smoke. 67 Atk means she’ll nuke most things and also activate Heavy Blade. So yeah, surprisingly tanky, super strong nuker, can Galeforce if you want, she’s got it all.
And if I were choosing a non-DB4 A Slot, it wouldn’t be SS3 either. It’d be Steady Impact or Atk/Spd Solo. If you can already one-shot pretty much everything, don’t bother quadding, and just use her weapon’s effect for defensive speed. Steady Impact prevents the QR effect from extremely tanky units who somehow survive her, and Atk/Spd solo would at least give her enemy phase speed to avoid doubles.