> also hiring actuaries/insurance specialists/consultants
What usually happens is that they pay a health insurer to "administer" the plan, or a "Third Party Administrator", which gains them access to all the actuarial stuff, as well as the provider discounts and negotiations, for a service fee, meaning the only effective difference is that your employer doesn't have its funds in a "pool" but can instead choose how much, or little to pay, from its own funding.
What usually happens is that they pay a health insurer to "administer" the plan, or a "Third Party Administrator", which gains them access to all the actuarial stuff, as well as the provider discounts and negotiations, for a service fee, meaning the only effective difference is that your employer doesn't have its funds in a "pool" but can instead choose how much, or little to pay, from its own funding.