I recently had some trouble playing while playing PvP on the airport map. It seems that you can´t hit every Hero from ervery position.
At this example I can´t hit his Razorback with my Dogface, because his always hitting the undestroyable post. I have to change cover first, before atttacking him again.
You already have enough disadvantages at this map if you are unlucky with Hero positioning and have to brake through the wall first to attack, so there shouldn´t be even more. Apart from this you should always be able to attack everyone from every position in PvP.