Does not matter if it is The New 52 origin it is not necessary to spend a year telling a story that is already being retold somewhere else. It seems Snyder never liked progressing the character now he doesn't have to.
Wasn't it Death and The Maidens by Greg Rucka that made Talia fully evil in the first place? I just assumed Grant Morrison figured that she was already a villain and just ran with it. He did say in Kevin Smith's podcast that we just witnessed love turn to hate. It is an interesting point that Talia witnessed Ra's in the pit more than once in her life it probably affected the way she views death in general letting her not see the full value of life.
Nyssa's torture of Talia doesn't seem to be mentioned much in the stories but I think it was big moment in Talia's history and does provide some explanation to as why her character went bad. To me it does not feel all that out of character that she is now evil.
I just see her relationship with The Heretic her own way of having Damian to love and raise he is a Damian that is fully his mother's son with no Batman or Dick Grayson to influence him.
@DMC: When Batman Inc started up during the last DC Universe Morrison did say that everyone would be crying by the end both Chris Burnham and Peter Tomasi have just said that they knew what would happen so it does not look like Snyder has anything to do with this.
With Damian's death ends a creative era of Batman it's clear that no one really wants this character to progress and change. It doesn't seem to matter that Batman is a character who has grown because of the changes made through the years it seems to be that no one even wants a Batman different from the eighties. Though if anyone was going to do it I am glad it was Morrison. Not looking forward to what comes after Inc. since the Batman books seem a little bland. Do not really like Harper Row and would not like it if she became the new Robin. There seems to be repercussions for the DC Universe I wonder if Trinity War is Batman trying to rewrite the timeline to save Damian. After losing both parents and his son Bruce should not really recover from this.