The TRUTH about Ascended Astarion, by me:
The moment you ascend Astarion he is at his very worst. The power he craved his whole life hits him like a truck and is so overwhelming he can't help but drown in himself. His heightened senses, and to quote him shortly after ascension, "My instincts are already so quick, the world seems slow around me." nigga is overstimulated to hell and back. He is horrible because he doesn't know how to handle these new sensations and his mind is filled with ideas of what he SHOULD do following the fall of the netherbrain. It is all too much and he is a grade A mess. HOWEVER with the help of Tav once again he can adjust back to normalcy. Just look at the epilogue interactions, he's still an ass, but he's in a much more relaxed place. This is because only Tav can tame him. And with her unwavering support in the early days of ascension, she can now shape who he becomes in the future. You do not fix him by ascending, but rather start a new game of "I can fix him" on a much higher difficulty setting. Bc honestly, fixing spawn Astarion is easy as fuck. Sometimes you need a REAL challenge and the ascension is just that. The ascension route is not his ending, but rather the beginning of a new can of worms that only the most loving and caring of Tavs can take on. Astarion will come to terms with his abilities, the joys of fatherhood, and the responsibilities that come with being a lord. He will lead an army of dhampir baby abominations, 30 to be exact, and once he and Tav reach that number Tav joins him in immortality, and they rule the city of Baldur's Gate and beyond, until the inevitable heat death of the universe. The ascension route is not for everyone. But the payoff is very well worth it.