The GOM operators follow the same regulations that the rest of the US follows. VSI indicators are not required in any VFR aircraft in the US. Whether that's good or bad, it is the law. Most helicopters in the GOM are actually better equipped than the average US helicopter. As GLSNightPilot said, US, European, and Oz regulations are different, and always will be. Throwing rocks at the regulatory agencies of other countries is senseless. In the US, it's perfectly legal to fly a single-engine helicopter at night, across cities, with no IFR instrumentation at all. There is no regulatory difference between onshore and offshore, except for the requirement for flotation gear. We have an entirely different philosophy than European countries on this and many other issues. That won't change. If you want changes, then you'll have to come over here and enforce your will, and I predict that will be resisted strongly.
Personally, I support stronger regulation and enforcement, but I'm also realistic about the probability of that happening, and mandating all twin-engine aircraft is not the best way to increase safety. Factors other than engine failure are what are killing us, and our passengers. Having all twins is fine, but better instrumentation, training, maintenance, weather information, and traffic information are all cheaper and more effective. Shorter working hours and more pilots are also likely to increase safety more than more engines. The amount of money that will go into safety is severely limited, and I want it to go toward the most effective fixes. More engines is not it.