Snyder tried turning Superman into Batman from the get-go with Man of Steel. He tried hard to make MOS like Batman Begins but it failed. Goyer is even more responsible for this. Nolan should take some of the blame for hiring Zack in the first place.
Then when we arrived at the sequel. You have a Batman-ish Superman facing Batman. So what does Snyder do with the help of Terrio (a non comic book reader)? He does what it takes to make Batman as cold and out of character as possible. Make him reeaaaally brutal, that way there's no confusion. The next order is to change Lex into a Riddler/Joker type, so the film has a bit of balance and personality.
I didn't mind a Superman who is more of an introvert at first, growing up. It would make sense considering who he is, how he can't relate to the rest of the world. But then i wouldn't use a Superman like this to cross-over with Batman. At least not until i show him as a more outgoing superhero in sequels. Have him become the Superman everyone knows, then bring Batman into it. That way you don't have to go such ridiculous, out of character extremes with the Batman, or an experimental take on Superman.
It's flawed from the get-go, because the whole concept of a more realistic Superman falls flat once you take a few seconds to realize that Superman will never be realistic. With Batman, there is always that possibility that a man can do this in real life. How far he lasts, what his gadgets are...that's up for debate. But it can happen because he's human. With Superman it falls apart unless you make him more like the comics as the series progresses. Otherwise you're dealing with a quiet, mopey Superman sequel after sequel, which ends up betraying the character and pissing off a lot of fans. It also makes people turn on Superman even more, no matter how badass you make him, because we live in a era where fun Marvel movies are delivering hit after hit. The general audience ALREADY thought Supes was boring. Now it's even worse because he doesn't show much range, humor, goofiness, as much warmth as the other versions, and he doesn't talk much. Warner Brothers shot themselves in the foot.
I also think a younger Batman would have been better. I think Goyer's original script was with a young Batman, because i recall him saying this in an interview. I also recall Snyder saying that Luthor would be a billionaire version of Brad Pitt. These original ideas were much better.
OH and that GRACE chick has always been the most annoying, unintelligent, idiot that's every been on camera.