So, I just created a new character and rushed to the first few enemy's to see if they could damage me with melee. And they could damage me with melee.
So I jumped back to my first character to see if there was any difference, but there was not.
Obviously still needs more testing but i'm fairly sure it has something to do with the Melee flaw that I picked.
I even respecced to see if there was any difference but there was not (because the flaw doesn't reset obviously)