J,
Same situation since time memorial there.....just stand your standby and if the weather isn't good enough or the MEL'd equipment (or defective kit not logged) is sufficient.....crank up....get almost out of sight of the runway/heliport and turn around saying the weather was too bad. Hold your explanation to just that. You tried but could not get there.
There was one 412 lost with all hands on one of those runs....that should be enough.
It is not life saving.....it is just another transport flight. The oil business used boats long before they used helicopters.
If you have the proper kit, accurate weather reporting, are familiar with the route, current and proficient in IMC and night operations, and have security at every stop along the way....and the weather is within limits then maybe give it a go.
The Life Saving release from the rules grants you the right to go.....but does not require you to go....if the management doesn't like it....throw the keys to them and point them to the aircraft.
The object of the exercise is for the crew, aircraft, and passengers to arrive safely without undue risk to any. If they will not live without immediate medical care....what chance do you think they have of getting that level care upon arrival in the dark?
A few hours waiting for daylight only makes the outcome much more certain....and safer.