Artifacts is something quite easy to address if you apply a systematic approach. I am getting nearly 0 rejects for artifacts for the last +/- 12 months if not longer:
- shoot exclusively in RAW , not too high ISO
- good exposure, particularly no underexposure, and no pulling shadows up
- very little or no sharpening when processing RAW
- if converting RAW to separate file before opening in photoshop use TIF not jpeg
What I am doing next with 100% of my pictures is applying TopazLabs DeJPEG filter (photoshop plugin). There is an old free version and there is up to date commercial one (which isn't expensive). The "official" purpose of the plugin is different, but it helps very nicely to remove that little artifacting. The key is to apply DeJPEG at very low settings, don't overdo it. I made several presets for different degree of artifacting/noise; and I am thinking about making a tutorial about that when I have some time.
When applied at minimal settings, DeJPEG filter smooths areas without detail while keeping details sharp, and adds a very little noise. This is an example (crop enlarged to 300%):
the version "more DeJpeg" not only smoothened stronger, but also has more noise added.