how could have been brought in midway through production if he wrote the damn thing?
He co-wrote it. That doesn't mean he sat down with Heinberg and they fleshed out the script together. That means that he got credit for writing some scenes that were added to the script Heinberg had written. Also, they started filming the movie before he was announced as joining the team. This is simply fact. Look it up.
EDIT: also Diana has killed under numerous writers. Rucka had her kill of Maxwell Lord in the run-up to Infinite Crisis.
I know this. I brought it up earlier in the thread, if you had bothered to read it.
Yes, she killed Maxwell Lord. Because, when bound by the lasso he said that the only way to stop him from using Superman to destroy everything was to kill him. And Diana, at the time, truly believed that there was no other option. But it affected her greatly. Even after she went to trial and the world court absolved her, she still stepped away from being a super hero because of that moment.
Diana doesn't just kill people, and she shouldn't just kill people and not have it affect her on a personal level.
Johns himself has said that he just didn't know how to write for Diana. And that's a fact.
Perhaps you mean that he doesn't write her in a way that you like, but thats different from him not getting the character.
Changing who the character is on a fundamental level is absolutely not getting the character, which, as I said, Johns himself has admitted to. The problem isn't that she's killing. The problem is that she's willing to kill anything and everything just for the hell of it, without it affecting her. She's not a bloodthirsty monster; that's just how Johns has written her time and again.
But you're write. He doesn't write in her a way I like, as an intelligent, interesting character. He writes a bland she-berserker. And that's not what the movie should be. But that's not what we were talking about.