Employers pay those costs themselves in return for rate reductions. Not sure how that differs from any of my other comparisons (auto, life, homeowner's).
I think you have to admit that one's health care premiums have nothing to do with that individual's "actuarial" risk to the insurance company. There is not a single form of insurance that follows that pattern. NONE.
As for the other, I admit health care insurance has its own peculiarities that make it a distinct field of insurance. And, no, your last assertion is incorrect. I have the advantage of having actually worked in the group pricing department of a major health insurer, so I'm not just speculating here. In lieu of further banging my head against the wall, I'll point out that the syllabi for the SOA's actuarial exams are available to the general public - just look in the "education" section of their site.
You obviously don't understand insurance outside of healthcare, if the insurance companies' underwriters and actuaries do their job right - the profit/revenue of all policy types is the same regardless of risk.
High risk=High rates, Low risk=low rates. Revenue/risk is balanced.
We all suffer spiraling healthcare costs because there is little correlation to what you pay for healthcare insurance and your overall risk to the insurer.
"Group underwriting" only exists in the healthcare industry - no where else.