There are many things that you could sum up as faulty or that could be done better in the BG3 story and cast, but this
Orin feels like a edgelordy serial killer ripoff of Harlequin.
is a totally wrong statement. In fact it has it all backwards. The seductive evil and cruel mass-murderer woman is a thousands-of-years old archetype in mythology and consequently fantasy literature. (Think of Circe, Medea, Morrigan..)
So they really nailed Orin very well as a Fantasy creature. One could see Harlequin as a superhero ripoff from the fantasygenre