UK AAIB reports 2010-2015
Here's some real data since 2010. Total of 44 reported accidents under "GA" with 23 PPL's, 5 student pilots, 14 CPL's and 2 ATPL's.
Of that lot there were 4 fatalities, which were 2 x CFIT (one a Gazelle driven by a PPL, the other a 109 driven by an ATPL). There was an R44 PPL inadvertent IMC and finally a new PPL mast bumping an R22.
Of the GA accidents there were 11 mechanical failures, 13 accidents through loss of yaw control/catch a skid/low speed mishadling, mostly in Robinson products and mainly very low currency.
So between the mechanicals, fatalities and low currency yaw control (which were hover taxi/landing/take off/parking events - I have been a little lazy lumping many of these together) that accounts for 28 of the 44 accidents. The balance were some flight instructor / student accidents, couple sling events and a couple of hitting bushes/tress whilst taxing.
In the same period there were 27 accidents reported under "Commercial Air Transport".
That also included 4 accidents with fatalities of which 3 (AW139 Norfolk, EC135 Glasgow and Sumburgh Puma) are yet to formally report and the other was the CFIT in central London.
There were 7 mechanical failures, 4 events of hitting objects on the ground a vortex ring heavy landing and a couple of loss of yaw controls.
You draw your own conclusions from that but personally I think it shows that there are actually more mechanical failures than anything else and the training to deal and recognise these failures seems to be effective as there were no fatalities as a result of them all across all licence holders and experiences.
It also shows that those most at risk of a CFIT are higher time pilots in more complex types and that if you take care of not hitting things on the ground and stay current such that you don't loose yaw authority you chances of rapping up a helicopter seem small!!
I guess the timings of AAIB reports seem important since any learning can be made sooner at the most simplistic level. For example if we believe the AW139 was a CFIT accident then it happened whilst waiting for the other report on the London accident. The formal report may have done nothing but it may also have been a timely reminder to owner and pilot..
If that is a stretch of the imagination too far then what about the odd example in 2012 where one company had two accidents inside a few weeks with slings - clearly the information flow wasn't happening internally so it was unlikely to be fed to other pilots doing similar tasks.
On the other end of things is the fact that whilst the events that end in fatalities certainly catch peoples attention regardless of the time scale between accident and report some of the other events may be lost in the mists of time.