Not sure how DHs will have a better idea without guidelines as to what is tolerable.
Ahh, you have reminded me of another quirk with the previous edition of RA1210. It had Tolerable as defined by the unhelpful deaths per 1000 population at risk per year and Tolerable in the sense of accepting the level of risk of doing something for the operational benefit doing it brings. E.g. it's tolerable to practice IMC flying by having one of the pilots external vision obscured as you gain the benefit of being able to fly on instruments in actual IMC. The DHs still understand what is tolerable in that sense, what they don't have to do is produce some dubious maths to meet an arbitrary limit that doesn't really tell you anything.
namely it can only be regarded as a risk to life if a death has already occurred
Not so, and if that's the impression I gave then I apologise, there are plenty of risks to life that haven't caused a death. Additionally the MAA Hazard Risk Matrix includes minor and major injury so you can have risk to life that you don't think will ever cause a death.
For the larger platforms (Chinook, Merlin and Puma) the fitment of fully integrated TCAS II systems is being considered.
In that case I'd assume the additional features of TCAS II weren't considered advantages for a support helicopter as they typically operate below the level where RAs are suppressed. But that's supposition on my part.
(1) The risks of collision and wire strike were the No.1 and No.2 Air Safety risk according to the Cdr JHC (ODH).
You'd need to look at the detail behind the headline titles to determine what that meant though. I.e. Wire Strike was likely to be concerned with horizontally strung power and telephone lines. MAC was probably concerned with hitting other aircraft in flight. The actual risk experienced fell under CFIT, and without knowing what the detail behind that was you can't jump to your next point.
(2) The risks, at the time of the accident, were neither tolerable nor ALARP.
That's not a fact, that's your opinion until it's tested in court. Just because an accident happens doesn't mean the risk wasn't ALARP, it's As Low As Reasonable Practicable, not As Low As Possible.