Larian added a little scene to the end of the drow orgy of all things. They sure can add a short animation of the pc walking towards Astarion's general direction after Karlach is dealt with, for those who choose to do so. He's right there behind some crates.
And change what the narrator says if Astarion is the only person with us on the docks. Neither me nor any of my characters would ever think "the guy who's been abused for years will be fine by himself because he's good at comforting himself, I don't need to go check up on him."
