What is back focus ?
The place where you tend to get really aggravated by some focus miss is with a portrait lens being shot at a very wide aperture. You focus on an eye, and the tip of the nose or an ear is in focus but the eye is a bit blurred.
It is important to appreciate this type of "misfocus" is usually because with the camera in portrait position and the outer AF points not being a cross type sensor, poor autofocus system accuracy is not uncommon.
An autofocus limitation with a few types of subject should not be confused with a back focus issue. A back focus issue affects all images. A camera which has a problem with a less than ideal autofocus subject usually focuses good with a better autofocus subject.
Many problems turn out to be a lack of intimate knowledge of complex modern camera equipment.