G'day fellas.
Just some thoughts from an outsider (ie non-USA, but EMS none-the-less).
Dog, it seems that you are trying to highlight the fact that all helicopter night/poor weather operations carry increased risk that ought to be studied rather than just giving one part of the industry that attention. In this I agree.
However, I also agree with the assertion that these were EMS aircraft employed in the EMS role. The fact that an Air Ambulance is not actually carrying a patient does not mean that it is not doing an EMS job. The EMS role encompasses the whole day - from pre-flight briefings, through training, stand-by periods, crew rest, earlier jobs (and their potential carry-over stresses), maintenance, admin etc etc. So, if a bunch of EMS aircraft begin to show an increased occurence of crashes, especially in a certain flight regimen, surely you agree that a study including all possible causative factors should be made as to why.
Now I know nothing of the circumstances of these recent accidents, but do we know if the crews' decisions may have been influenced by EMS-specific factors? Perhaps they had just performed a particularly harrowing job, or were under pressure to return to base to perform another job. What were the cultures of the opperations in question with regards to turning jobs down due to poor conditions, or allowing aircrew to be possibly pressured by medical factors which, whilst important, do not change the fact that some flights are better left until flight conditions improve.
My point is simply that EMS is differant from other ops in that the life and death pressures can impinge on the decision-making process of the aircrew. I think perhaps a study of training and equipment suitability and CRM knowledge levels of flight, management AND medical/tasking personel would be a good place to start considering the fact that there is a perceived increase in accidents of aircraft engaged in EMS tasking of some kind.
Just my two bits from a down under EMS/fire operator.
Cheers