In all the discussion it should not be forgotten the 42 is a very new design and so is much of the technology.
I am not making any excuses for what may arguably be faults in the design, but I wonder whether the 42 is any more or less prone to the odd design fault compared with aircraft of yester year or whether the testing is less rigorous than in the past.
I have getting on for 50 hours now on this type and am in no doubt all of those hours have proved invaluably in understanding the systems, and in particular the emergency procedures. A number of other "issues" have arisen during this period and I know that Diamond have in hand a few modifications.
However, as others have said, the POH on this particular issue is in my view quite clear. If the pilots had followed the POH they would not have allowed this combination of circumstances to cause the failure. I cant imagine in any twin that you would not consult the POH before a ground start after a flat battery.
I think it does however reinforce the importance of having the POH with you if you intend to fly more complex types. The G1000 instrumentation provides a far greater range of fault finding information than conventional instrumentation, and by its very nature has greater propensity for unfamiliar faults to arise. Personally I wouldn’t go anywhere in a 42 without the POH, and also the supplementary manuals produced by Garmin and Diamond. The fact of the matter is they are all available as a PDF if you want to keep the original safe and are really not that bulky.
Without the POH a GUI annunciated fan fail will grab your attention mid channel in IMC and you may have no idea whether one or other or both of the glass screens is about to overheat or what actions to take. In fact your concern would be completely misplaced about either screen over heating, but you might well be excused for jumping to the wrong conclusion.
However, and all that said, the POH could in a number of cases be more descriptive of the fault background and more specific as to actions to be taken and why. For example a GUI fan fail may either mean the blower to the avionics bay has failed or the fault reporting circuit has failed. The POH gives little information of if and in what circumstances the avionics are likely to overheat and if they do, what the consequences are, other than a comforting continue the flight but have the system inspected when next on the ground.
Another good example is the consequence of an engine failure. The POH is silent on whether or not the autopilot can be used single engine. You would have thought anyone flying a 42 would want to know before their first flight.