AF issues/out of focus shots with the D7000

I frequently end up with soft & out of focus shots like these:



I'm using a D7000 with the 18-105mm VR lens. From what I've observed, it usually happens on shorter focal lengths, when the subject is zoomed out.

The AF settings I use are: AF-S single point. All these photos are shot through the viewfinder (not in live view mode) with the focus point on the subjects face.

I've uploaded the original JPEGS from the camera; I also have the RAW (NEF) files for each of these photos, please do let me know if they're required.

Is there some problem with the AF module in the camera or there's some deficiency with my technique or AF settings.

Would appreciate some insight and expert comments.