"As you know helicopters can fly slow enough to enable the pilot to see ahead. You gave the vis as 1500 m. More than enough."
That doesn't mean that you have to do it. Below a certain speed (which in a Dauphin is 76 kts, but which more generally is 45), the stabilising surfaces aren't working. If you are a typical PPL who thinks that the instrument appreciation that you get on your course is the equivalent of an instrument rating, and that was over two years ago so you are definitely not current, you will be dead in about 178 seconds (Australian figures) if you suddenly pop into an unseen bit of cloud.
Because of the above, my own personal limit is speed based rather than vis-based - if I'm having trouble at 60 kts, that's when I put it on the ground.
Phil