A lot of good discussion, as always on pprune.
One of the issues is lack of knowledge of why we do things the way we do them.
I think that hover power plus 10% is a good way to do things, but it's not always a practical thing to do. And we don't have much guidance for the 'non-standard' situations.
At the risk of changing the direction of this thread - might I suggest that part of the problem lies in the lack of a low airspeed indicating system couple with the lack of knowledge of the performance characteristics in that region.
For example, no helicopter I've ever seen has a maximum angle of climb airspeed published (fixed wing do) - the reason is that it changes from zero (with lots of power to spare above hover OGE) to something else as the power required edges up to the power available. Not only is there no flight manual guidance for this, there is no academics for it, even at test pilot schools!!!
There are times when hover power plus 25% is the only way to go, and other times when hover power is all you have. And we don't teach people well about understanding the difference.
A window of opportunity for someone clever with helicopter performance and computers, methinks.