I've always found it strange that when you find someone on a head glitch, and you start shooting - how come if you get loads of hitmarkers and they manage to kill you? I mean you're shooting them in the head it's the only thing showing is the head of the player. They should be dead if you manage to get hitmarkers on them.
I know what your saying but there are other factors coming into play. How much of his head is showing, how much of yours is. Who is landing the best shots, who has the stronger weapon etc.
what I do when I encounter someone aiming behind something is if I get a hitmarker or two (I move back to reposition myself) its no use dying trying to kill one person.