I think the relationship between a Dark Urge and Astarion is very deep and intense because they are so similar and understand each other.
Originally Posted by Sini
On the night you are supposed to kill the person you love, you are not yet in a relationship with Astarion, but the conversation is one of the most beautiful conversations between them and later Astarion says for the first time that he cares for you and that it is worth the risk is.
Actually you can be in a relationship with Astarion on that night! I was and my DUrge got a Disadvantage on lying to the butler because of the romance. That scene is so good, I was sweating from fear of missing a roll.
I agree with you, the romance with DUrge and Astarion is the most intense and romantic. I really love it. IF I play it one more time I will have a hard time not picking DUrge and Astarion again..