I used this to test: http://regex.info/blog/photo-tech/focus-chart
The lens seems fine so not sure why I'm getting so many out-of-focus shots.
The test chart is fine as long as its printed at a low contrast to be certain the AF locks on. I've used Jeffrey's charts many times, and I'm a fan of his. Once FoCal became available, it is far easier to run and provides more information.
One thing he misses, is the part about covering the eyepiece while your camera is on a tripod. That avoids erratic results.
Jeffrey's chart and instructions are for checking front or rear autofocus, but he does not dwell on the proper distance, just mentions that lenses will front focus near mfd.
If you get consistent results when resetting the camera lens to infinity before each of several shots, then the problem does not reside in the camera or lens, but rather in the settings you use.
The default settings work for almost all cases, so only change them when you are certain a different setting is needed.