212man
You have to remember that the NTSB staff are not used to analyse and draw conclusions. The Board members do that, and they look at 30+ accidents per meeting. Unless a public hearing is called, discussion is very limited.
Sox6
There is the following conclusion in the JHSAT 2006 report:
Improve Quality and Depth of NTSB Investigation and Reporting
Many accidents are not receiving in-depth, onsite investigation by NTSB investigators. Investigations are being performed by telephone interview or by personnel whose primary function is not accident investigation. Increase the degree of Human Factors investigations to include detailed personnel information, and assess the extent of operator oversight.
This was related to 76 of the 152 reports analysed! The PHI S-76 suggests the rest aren't much better.
The punchline is that the FAA were on the JHSAT team (unlike the NTSB), but it is mostly FAA inspectors who are the "personnel whose primary function is not accident investigation".