Some interesting discussion here, but you have to look at the whole picture to assess the risk:
1. There will always be unmarked wires - period. So location systems relying on the position of marked wires will always have a vulnerability. Also when operating low level there shouldn't be too much taking your interest inside the cockpit for any length of time, so the 6 P's are critical for this (see point 4).
2. Helicopters have these really cool things called Pitch Change Links or Rods just below the rotor head. If any wire makes it up the cabin roof to this area you are going to have a really bad day. It doesn't matter how big or heavy the aircraft is, these are an accessible and deadly point of catastrophe. This is why you need cutters or some form of deflection away from this area.
3. The type of wires in this accident (11KVa strung at about 30' or less) cause the majority of wire strikes. The poles are often in the trees, the wires turn green soon after hanging and the distance between poles is irregular depending on the terrain/topography. If you regularly fly low level and don't anticipate or mitigate this hazard, your risk score went up considerably.
4. Before training low level, (when possible) it makes a great deal of sense to do a slow, medium height route recce to clear the hazards before getting your adrenaline fill at 120 Knots and 15 feet.
5. Operationally, you may be on your own in terms of wire and hazard mapping if you are in an distant or unknown area, but on operations we have a higher risk level not necessarily acceptable when training.
Low level flying is an operating environment that demands complete preparation, full attention and situational awareness. Hazard mapping systems don't change any of that and wire cutters will only save your life after you've got it terribly wrong in the first place. I'm fully supportive of both of these measures, but they are fully effective only when, as professional aviators, we have taken all the preventative planning and operating measures we can before descending low level.