This is kind of hard to explain in words, so you need to see pictures of this first. I would say that it is a major issue, as it affects gun play and may get you unfairly killed. It is possible to hit yourself even when the gun barrel is nowhere close.

Pictures here: https://imgur.com/a/zpvUgTq

In short, the gun aims in the totally wrong direction. When I look straight ahead, the gun will go into the sky. It looks similar to when you aim up and use "Alt" to look down, but that is not the issue. When you shoot with the gun poitning up, the bullets will still go to the middle of the screen, in totally wrong direction. Does bullets shoot out of the players eyes and not out of the barrel in DayZ anymore?

In the pictures, you can see how the bullets even can hit behind the gun when laying down etc. The bullets can also hit the ground if I aim straight forwards.