Hot damn I'm really considering killing this asshole or sending him back to Cazador,
I'm kinda bummed that he was "evil" from the start, really thought he had potential, but from the way you described that article it seems that he was never a good egg.
As I previously said, I'm not sure if Larian is still going for this backstory when it comes to Astarion, but this seems to have been the case for demo version back in Februray. Here is the full quote in regards to that:
And you can read the rest of that article here.
So, if this backstory is still valid and unchanged, then in all honesty I can't say that I feel bad for what has happened to Astarion. If anything, what happened to him is very ironic.