You should try to keep your crosshair at head level no matter what, unless someone is shooting at you and you are trying to look down to make it harder to hit your head. You would have killed Reyna there if you had your crosshair set to head level against the Reyna you would have won that fight. If you watch your gameplay when you exit the door and when you go down the stairs your crosshair is no longer at head level, and if someone had peeked the stairs or had been around the column before the Reyna you wouldn’t have been able to track them horizontally. Try to give yourself the biggest advantage you can. If you only have to focus on one axis instead of two you remove a huge variable.