But here's another question: are these choppers designed from the ground up for offshore applications? If they are, then any accident as a result of technical failure can only be seen as a failure of the aircraft and its manufacturer: it is simply not fit for purpose. If the answer is no and these choppers are modified to operate in world's harshest environments (i.e. offshore)...
Firstly, I would argue that the offshore environment is by no means the harshest that helicopters operate in. As an example, a 70 kts wind creates a very harsh environment for people trying to work on a platform and/or plane and deplane from a helicopter, but for the aircraft itself it's a totally benign situation.
Secondly, it is not realistic for helicopters to be designed for one role only in the civil market, with its relatively (compared to the military) low production/sales volumes. The 225 is a variant of a military type but how that is relevant in this context is unclear to me. Other types such as the AW189, AH175, are designed for the civil market but have to capture a range of operations across a wide spectrum - air ambulance, police, SAR, VIP etc. but, again, it is not clear in the context of your assertions why that has any relevance.