The human performance factual report is an interesting read, describes the training received. Both pilots paired together for initial and recurrent training at NETC. Came as a complete surprise having read the CVR transcript first.
Departing from that helipad, with aircraft lighting (if they could find them all) and the ambient cultural lighting should have been easy. Did it all the time EMS with the 222 (UT with no stab) and later on offshore, but you have to able to accurately control the helicopter and read the attitude instruments. Like Crab says, no biggie if you know what to expect and have done it a time or two before.
I see Talbot was part of the investigation team from Leonardo, met him when he was doing icing trials on the 139 in Alaska. Sharp guy.
I've flown helicopter Caribbean - Florida a few times. Totally wallpapered with permits, flight plans, customs notifications - all due to my healthy respect for foreign authorities and especially the US CBP. But they sound like they flew regularly to the "island" and back without any notification to any authority. The flight plan discussion only came up for the return flight due to some realization of an ADIZ penetration concern and an ambulance call out.