I did it the old fashioned mass murder way, so no Halsin for me. I'm basically redoing an older playthrough that itself got murdered by patch 5. I got to the middle of Act 2 in that one. Poor Minthara was not doing well in the bug department, and talking to her as Astarion was kinda sad because he really gets her, but of course Larian didn't give them any special dialogue.
I'm going to do it too. I'm trying to make all the choices I think Astarion would make, remembering his comments, suggestions, approvals and disapprovals from my Tav playthrough and vids. I found his and Lae'zel's banter about obliterating the grove after visiting it for the first time rather funny. That
is sad to hear that there are no special lines.

The choice to convince Halsin is something I'd like to have for other playthroughs.