The vast majority of emergency medicine is not emergency medicine, but emergencies are among the most likely things to have a catastrophic impact at the individual level. I cannot possibly treat the entire complexity of healthcare in a single comment and neither can you. That's why I'm offering a limited specific counterexample to your general argument, to point out the existence of fundamental economic problems in healthcare that are often buried by economic jargon which misrepresents the behavior of the healthcare market.
As RAND and Oregon show, free and reduced cost healthcare do not minimize avoidable suffering (at least suffering caused by medical conditions) any better than high marginal cost plans.
Unless you're poor or chronically sick. You have made it abundantly clear time and again on HN that you do not believe in altruism but think that all economic decisions should be made on the basis of self-interest; I think that approach is bunk and so we are not going to agree on a common goal any time soon.
Can you provide an argument why a more efficient medical system - specifically one where patients don't visit the doctor for frivolous/moral hazard reasons - would be somehow susceptible to black swan events?
If you're maximally efficient there's nothing to cut when the shit hits the fan. I think critical systems should include some excess carrying capacity (ie waste) because it's faster to reallocate resources internally than to get additional resources under time pressure.
As a simple example (from which I am not attempting to generalize to the secotr as a whole and which I am not going to get into any nitpicky arguments about), there's a good argument that we have a bit of a doctor shortage these days: https://www.quora.com/Why-dont-we-train-more-doctors
It would be rather inefficient to have a public health system with too many doctors and nurse practitioners. They wouldn't be as busy and wouldn't make as much money as they could at equilibrium, and you can easily imagine various second-order effects of such an inefficiency, and the fact of a cumulative social cost.
But if there is a public-health crisis, would you rather meet it with too many doctors or too few?