All in all, I would say if they wanted to keep Dany's character in line with how she was, the final should have gone like this.
When they ring the bells, she hops over to her men and says "no one else dies unless they raise a sword to you. But the people who ordered this defiance will burn, all of you watch what happens when you defy a Targaryn (Or whatever, I'm sure an actual writer could produce better dialogue)." Then have her fly up, and burn down the red keep with Cersei and the other nobles inside. Like full on, fuck you burning.
Still ultra violent. Still skirting with her being too sadistic....But not crazy genocidal. That's in line with Dany's temper and viciousness. You still get a lot of the drama, its shocking she killed so many upper class who were also innocent, its shocking she burned people alive, but its not indefensible like burning up mass civilians is.
They were just going extreme for the shock factor, I think, and it played poorly. Dany could have easily been shocking in character, there wasn't a need to violate her character like that.