Not taking in to account the first 30 creepy minutes...
Bolland art made the comic feel like a piece of art, on the other hand animation and art style was pedestrian.
I think the story was supposed to be out of continuity like DKR and Arkham Asylum ( they even show a pictue of golden age Batman, Batmite and GA Batwoman in the cave, wich didnt made sense in the post crisis 80s were the multiverse was wiped out of existence).
So its possible that Moore's original intention was to kill the Joker, but the book was adapted in to continuity so Batman didnt kill Joker in the official canon.
edit:
I maybe wrong here but i think Barbara didnt even exist post crisis, since in Year One Miller made Gordon the father of a son and not a daughter, at the time DC was moving out of campy comcepts like Krypto, Batgirl and Supergirl. Someone may correct me here but I think TKJ was Barbaras first appearance post crisis as the story was adapted in to regular continuity .