Depends on the reason for the new or revised rule: loss of life/potential loss of life?; crew-pax-aircraft safety?; Grow the industry? Protect the industry? And so on.
Now whether the root cause is “good enough” or the “cost offsets” are acceptable to everyone would depend on their objectivity/experience on the goals of the corrective action goals vs my objectivity/experience.
So it sounds like the idea that there should appropriately be different responses depending on both the severity of the harm or possible harm and its certainty is an idea that agrees with you.
If that is correct, I would like to consider a set of related non-aviation examples to help clarify. These are from everyday life. Let's consider the following 4 situations:
Situation 1: I hear from neighbor X that neighbor Y yells at his wife all the time.
Situation 2: While walking past neighbor Y's house, I often hear him yelling at his wife.
Situation 3: I hear from neighbor X that neighbor Y has threatened to shoot his wife.
Situation 4: While walking past neighbor Y's house, I see him holding a gun and threatening to shoot his wife, who appears completely non-threatening.
I assume you would agree that these four situations differ in the morally appropriate response.
In both 1 and 2, I think one morally appropriate response would be to simply never deal with neighbor Y and avoid him, particularly if I don't know him well.
In 3, I think a morally appropriate response is that someone try and intervene, maybe contact the wife by other means to confirm.
In 4, I think a morally appropriate response is to draw my weapon and shoot neighbor Y.
Now I know you might not agree with my exact moral reasoning on the responses, but do you see that it would be appropriate to distinguish between 3 and 4 in terms of what one does? Whereas in 1 and 2 it doesn't matter that much and that the same response is likely appropriate in both situations.