Well today on PC, just after I landed I saw an enemy Revenant picking up a gun right in front of me. I had no weapons, so I began to punch him. He shot several bullets but didn't hit me once, and I downed him as we were jumping off the building. I think that, if you know what you are doing, you can knock people down. But I honestly wouldn't tread on that.
Now on console, I find the punching annoying. Its so damn annoying when you try to shoot someone at point blank range, and instead of shooting your legend starts punching. You have no idea how many times I have seen other people doing this and then get knocked down because of that.