Well, yes, the AAIB do voice opinions on maintenance. The recent fatal Sandown PA28 crash, with the well trashed engine, is one recent example. But the CAA does nothing about this, evidently, which makes the AAIB's views worth next to nothing.
The AAIB Sandown report made reference to the well known Lycoming camshaft wear problem but I don't think they implied it was the cause of the accident. As you know the only test required on an engine is the differential compression test and although the cam might be worn in can only be detected by metal in the filters or by removing a cylinder for a visual inspection. I always felt that the 5 minute climb test embodied in the 3 year flight-test was the most useful part of the process and good for detecting poor performance, however this is no longer required under EASA rules (what about the FAA?). What I'm trying to say is that it would difficult to blame a maintenance organisation if compressions were good and there was no metal found in the filters.
Have you or do you ever carry out this 5 min climb test and compare the results with the POH performance figures??