Tartare - in simple terms, a helicopter uses more power to hover than it does in cruise flight and so speed is your friend.
If you haven't got speed but have the altitude to dive on speed, then that is also your friend.
The difference in power required from zero airspeed hover to 15 to 20 Kts IAS is very marked and so, coming below that speed without having sufficient power to hover is going to cause you problems - as in the Colombian accident.
He could have made a steeper approach, all the way to the ground without coming to the hover at all - the brit mil call this a zero speed landing - but he would have to offload pax before trying to depart.
As AAKEE says, the winds around hills are often at odds to the main flow with up and downdraughts and turbulence - that is why HOGE power isn't enough, you need a thrust margin to allow for those factors if you want to stay safe.
Gordy - your technique actually seems very similar to the LDP for many PC1 profiles.