Since you can stack your ATK^, the best way to fight ALL the Dominas IMO so far:
1. Turns 1+2: Fury of Llavanya
2. Attack for 3 turns
3. Refresh your ATK^^by casting Fury of Llavanya
4. Go to 2.
If Katrina Bitch Slaps you, Use Fury of Llavanya next turn to refresh your stack and go to step 2.
Soul Link scales to ATK so with your ATK^^ it does good damage and heals for more HP.
Sword Flash is a pretty good tool for Katrina. The effect it has on the Dominas' hit/miss rate is... pretty hit or miss (weird, right?) but Sword Flash can still poison Katrina with the Doomblade of Bruh.
Never a bad idea to go Shadowbound if your HP are low. Hell, if you've got the MP and a fresh ATK^^ you can use Soul Link on the 3rd turn while in Shadowbound and get a few MORE turns.
Depending on what you wanna do in the fight you might want to spend a few turns building up TP before starting the sequence. I was able to beat Narcissa 2x in sequence by using Llavanya's song at the end of the first fight so I had some MP to go into the fight in her vault. (Still had to use a cleansing potion to counter the poison... don't know why I hate using potions so much...
)
If I was Dekarous, I'd be revisiting some of these skills or trying to create Domina mechanics that circumvent some of these strategies. Seems kinda cheap to me that the same tactic works so well on all of them. I know he intended Narcissa to be beaten by her weakness to ice, but you don't have to go that way.
Note: the bruh sword is actually different from the Doomblade of Bruh. With a save editor you can get the bruh sword (+500 ATK) and
really break your game
EDIT: This got me thinking... I tried and you can actually spam Shadowbound,=>Surrender (Full TP)->Llavanya's Melody(Convert 100TP to 250MP)=>Soul Link=>Soul Link and repeat forever with the Golem Sword equipped... gotta fix that.