I think the relationship between a Dark Urge and Astarion is very deep and intense because they are so similar and understand each other.

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.

When it comes to the story of the Dark Urge, you shouldn't forget what the Urge actually is and the Durge cannot defend himself against it. Before the dagger in his head it probably didn't matter to him but now he can of course say that he doesn't want that and defend himself and Astarion will help you, because he know what you feel.

Personally, I can't play anything other than Dark Urge, preferably Drow and Bard. I prefer to play alone with Astarion, the rest can stay in the camp. smile So he has even more texts that other companions might otherwise say.

"Now, was that civilized? No, clearly not. Fun, but in no sense civilized" ~ Braingremlin