HC - this is partly how I earn a living - the numbers for helicopter transport are that bad....
One would have hoped that defect tolerant design codes would have lead to an improvement - but they have not - at least in the present incarnation. I'm not sure the certification inself is the real reason. For instance JAR approvals for a new engine are quite modest - but of course the certification process and approvals engineers can have a huge influence in terms of 'opinion engineering', drawing things out by insisting of often irrelevent justifications - and that leads to manufacturers doing everything possible to avoid the certification process. Hence the re-treading of earlier 'successful' designs with numerous mods.
Shytorque -- yes the information to date does suggest a QC issue - but underlying that are design decisions - this is a 'low duty' shaft with appropriate levels of design detailing. Titanium studs would be another. At the end of the day it all rolls up into an overall incident rate.