As sad as I am to see him leaving the project, I'm also a little relieved, as I'm still not convinced how well a Wonder Woman movie would be. It seems like it would be stepping into "Hulk" territory, where most people only know the character from the TV show, and if it's any different from the show it just doesn't work. I wouldn't want to see Joss' reputation sullied by a failed WW movie. That said, he's probably the only one who could do a half way decent movie, and we may now be on the path to a movie of "Catwoman" sized failure.
Batman you can make cool, and is pretty easy to represent on screen. Superman can work, as has been shown. I just don't know how you can do the visual of Wonder Woman on screen and not make it goofy looking. Maybe they should just save her for a Justice League movie, where she would be in a crowd of colorful types and wouldn't look as out of place. Just thinking though.