MALENIA DOWN BAYBEEEEE
Spent a long time getting it down, but eventually landed on a really cool rotation of hitting her with a Black Knife projectile to offset her heal --> back up to let Luthel draw aggro --> hit her with Dragonmaw to knock her flat --> switch to Coded Sword and Unblockable blade to stagger her --> switch back to Black knife and critical hit and to deal a bunch of damage and double proc Assassin's Crimson Dagger to double heal.
So satisfying to piece this all together, it was a great mechanical cap to the game for my character.