No POH of a twin engine helicopter is going to tell you to ditch with a single engine fire - unless you can't put it out. You carry out the immediate actions. Then when you are in a safe flight mode you do the follow up actions.
I had the privilege of being a sim instructor not so long ago. It was a privilege because I was able to see how a cross section of pilots with different backgrounds, experience levels and cultures coped with emergencies in periods of high workload. Most pilots cope quite well with an engine fire in the cruise.
Give them one on finals to a rig at night in bad weather and that is when the problems start. The ones who ended up with a red screen were the ones who tried put out the fire and continue with the landing. Mostly this happened because the flying pilot was concentrating on the landing and the non-flying pilot shut down the wrong engine. Or the flying pilot's attention was diverted between landing and confirming the correct fire drills and messed up the approach.
The ones who eventually diverted or landed on the rig safely OEI with the other secure were the ones who carried out a missed approach and did the correct drills.