The AAIB Sandown report made reference to the well known Lycoming camshaft wear problem
The well known Lycoming camshaft wear problem isn't going to make 40% of your cam lift disappear up the oil filter, without somebody noticing.
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??
I partly agree in that the pilot should have spotted the fairly obvious shortfall on the book performance, on takeoff, at any time during the preceeding few years! My feeling is that a number of people dropped the ball on that one, over some years, including the final day.
I do the climb test every time I fly, making sure I get the right FPM. The 5 min climb is difficult as I would get done for busting CAS. Also, on takeoff, I check the MP, 2575rpm and the expected 23.6GPH flow rate. With instrumentation, one can see something isn't right.