I agree with the meaningful part- perhaps not in the way you mean? To me I get this feeling that the epilogue doesn't come across as... Astarion-y, at all. I only got that impression from his interaction with a friend Durge, and what he says when Cazador's still alive and kicking also reminded me of his sadder moments in the game, at least. The rest feels so very bland I can't see the character shine through all that much, only because he's visually there and making the same sounds.
My impression of him was of someone being exuberantly giddy to cover up the feels they have. Might also be my interpretation because his overheard dialogue is mostly him being nostalgic, annoyed that there isn't any blood on the menu or him worrying about the other spawn, if you went down that route. All of which, lack of substance aside, stand in contrast to his mood during the actual dialogue.
As for meaningful, I would expect an epilogue to be a story wrap-up. So I'd want to know how the ending we picked has influenced our lives together and how issues that were left unresolved at the end of the game got tackled in the time that passed. If I play an origin, I would also like some options for my own character to deal with their stuff. Part of why I am such a fan of the vampire book-club ending (It's an ending Avatar-Astarion and Gale can have when the other spawn are alive - for those who haven't read me gush about it.) is because it allows both characters to be vulnerable about their remaining insecurities and offer reassurance to their partner. This helps to get the "there is nothing we can handle" sentiment across while in Astarion's dialogue, it just remains a line. There are no hardships to overcome.
He does at least seem irritated by it, but not nearly enough, and just the fact the line is where it is feels like the game thinking that's actually a perfectly okay thing to say.
Yeah it's weird. I am often puzzled about who the game implies the player character to be in Astarion's romance, and I find it fairly hard to paint a consistent picture. What I mean: What type of person would think this was a good thing to say after the graveyard scene and the follow up dialogue in the morning? Someone with wax between and in their ears most likely ...
