Direct from the features list:
I think a lot of other people have made the same mistake.Combat permissions in tribe zones based on tribal settings
This really is going to change things for a lot of people I think.
There's not much point to building a defensive city if you can just turn off the combat, and if some people can turn it off then I see pretty much everyone keeping combat out of their city.
I don't feel mislead, I made this mistake myself and blame no one.