A body shot with a Scout Rifle only does 33% of the damage a headshot does. For an AR, a body shot does 41%. And it depends on the situation. If your in a relatively safe spot, yeah, it takes more skill to land a headshot with an AR. But that's hardly common in PVE. Most of the time your surrounded by hordes of enemies, and taking the time to line up that perfect shot can get you killed. With an AR, you point, shoot, and chances are, you are going to land a few headshots from a clip while you can keep on the move. You can't do the same with a Scout Rifle.