I made my comment just to remind folks that our use of terminology can present false impressions as despite the 212/412 design as both a Combining Gearbox and a Single Driveshaft from the C-Box to the Main Transmission, it has been a very reliable Twin Engined Helicopter.
The same can be said for the Chinook and Phrog with their Gearbox designs and Sync Shafts.
When it comes to helicopters we will never have complete "redundancy" as there are too many "Single Point" failure points that will take the whole thing down.
Those that see Single Engine Operations over water as being a "Sin" should really look at the Statistics and see if their position holds water.
As in most things in the helicopter business there are combinations of factors that must be considered when making decisions about what type of aircraft to operate. Numbers of engines alone is not the full Monte.
I would suggest the 212/412 series of helicopters are well proven and reliable although in the strict definition of a Single Engine Helicopter, they might well qualify.
If One were to be very strict in One's thinking every helicopter has a combining gearbox in the form of the MGB which has an Engine input for each engine. Despite the individual Inputs which have Over Riding Clutches of some design, the single Transmission makes that Single Point for failure.