Does the typical Lean Six Sigma training need to be expanded?

Lean Six Sigma training focuses on the identification and removal of chronic problems. The tools set provided in most curricula is not very efficient for finding causes for isolated special cause events that come and go.

I see four general problem solving methods in use today; Six Sigma, Lean, Root Cause Analysis (RCA), and PDCA based continuous improvement.

Traditional Six Sigma tools are efficient and detecting and solving chronic capability (quality) problems in both stable and unstable processes. Great for the improvement processes with lots of data.

Traditional Lean tools, which are not as driven by data, are improvements that make the process more “Ideal” and simple. Great for processes with limited, if any, data. They are very efficient in improvements where the process quality is adequate, but it is too slow or too costly.

Traditional Root Cause Analysis are based on a logical questioning of what occurred, when it occurred, and what else was going on. These tools do not need a lot of data and can use observations and qualitative inputs. These tools are quite efficient at addressing momentary or infrequent problems that are not part of the standard process.

Traditional Continuous Improvement focuses on the PDCA (the Deming Cycle) or PDSA (the Shewhart cycle). Where a close observations of the process will identify small incremental improvements. Over time, this can address nearly any problem that can be quantified, but it is slower than the other methods.

Lean and Six Sigma were blended together by the top providers about 5-6 years ago. Is it time to teach RCA and PDCA based problem solving too?

What do you think?