ACAS Bulletins
ACAS II | Eurocontrol
Referring to the above several bulletins, it is not recommended to innitiate any avoidance maneuver based on visual or TA only information.
More is said about not trying to avoid a traffic by turning, horizontal avoidance.
And that in of itself is part of the problem, one size does not fit all, what is a practical and sensible procedure in hi density airspace is rather cumbersome and overly prescriptive in sparsely populated airspace where you might be lucky to see any other aircraft.
Quite frankly this kind of incident happens on a fairly regular basis in various parts of Africa and IMHO you would be an ass to wait until you got an RA before initiating any avoiding or mitigating action.....and yet there are many many flying around that would happily hang their hat on the eurocontrol guidance purely because it's written down and quantifiable, rather than being this nefarious and outright dangerous concept of airmanship.
It's the same kind of mindset that makes some happier to penertrate convective weather as they wait for a clearance rather than exercising sound judgement by avoiding the weather and filling out a bit of paperwork afterwards.
I know it's a bit of a drift from they subject matter here, but it's all part of the larger picture.