I have a three tooth lockring tool which provides better traction than a single toothed tool and once I know the cog is as tight as it can get I engage that tool and make sure that lock ring cannot get any tighter.

Have never had lock ring or cog failure and although I always run a brake have no worries about doing hard skids and having things fail in the back.

Conversely, have had people get their bikes from reputable shops who did not seem to know how to properly tighten a cog and lock ring and because of this, people have experienced failures.

In most cases, if a shop did the installation they have been good to cover the damages.