Well the main problem with Astarion for me will be that my Paladin will most certainly NOT tolerate undead in party ... or camp as the matter of fact. :-/
I agree that lack of Dex-based followers is a problem ... But its even worse that the only one we have at our disposal is ... well, this. :-/
Well archliches are a thing, a paladin doesn't necessarily have to kill all undead, and undead arnt nessicarily all evil.
The biggest issue is Astarion leans into the melee biting vampire thing