The reduction in gun death rate would drop for domestic violence, while beatings, knifing and other such things would go up some and gun deaths due to crime would increase because criminals know you can't have a gun to protect yourself with. Additionally the government can now take control of every aspect of our lives with militarized police forces without threat of any rebellion because the public is disarmed.
Let's hypothesize that I want to kill you, my access to a gun or not doesn't effect the fact that I want to kill you. What a gun ban would do is prevent me from legally obtaining a gun with which to kill you. How much of a barrier to entry is this ? If I want to kill you but can't shoot you with a legally obtained gun what are my options? I can get a gun illegally, I can hire someone to kill you, I could poison you, I could use some other kind of weapon, I could stage some kind of "accident". In short, I have any number of potential ways to kill you, if I have decided I want to kill you.
The heart of this argument boils down to how many gun deaths are there simply and solely because there is a gun available? This question is nearly impossible to predict accurately because if the intent to kill is present there is no way of knowing how far that intent will go or if it will dissipate due to the minor hurdle of not having a gun on hand.
Also a gun ban would not stop gun crime because criminals will get guns if they want guns.
So what we are looking at is the minor potential to maybe prevent some domestic gun related deaths weighed against a lot of negative outcomes that are very real and it doesn't seem like a solid choice to ban guns in light of the heavily negative effects a ban would have.