I find it interesting that Heard was defending herself by saying she wasn't punching, only slapping/hitting. I assume she means that a punch would be DV, but not a slapping.
However, I think we'd all agree that a man slapping a woman would be DV, mainly because of the greater risk of injury as there is a different in strength.
Interestingly, I managed to stick my beak into a DV situation about a week and a half ago. I saw a couple arguing in the street. She was screaming at him, grabbing and hitting him, but I didn't want to get involved. Then she headbutted him, solid connection and it rocked him, he had to go and sit down. As he did so, I asked him if he wanted me to call the police, to which he said yes please, but as soon as they realised I was actually speaking to the police, they held hands and walked off, despite her continuing hitting him while he was sat down. I'm annoyed with myself that I was going to let the hitting go and it needed a headbutt for me to act. On the other hand I have intervened when I've seen males squaring up and simply acting aggressive, no actual violence.
I guess what I'm work out is that if there is a higher bar for women to commit DV, could this be a reason for the difference in violence towards the different genders?