If a life insurance company asks a health plan to disclose medical claims information about a decedent for the purpose of providing death benefits, must the health plan require the life insurance company to obtain an authorization under HIPAA from the next of kin, executor of the estate or from a person responsible for the decedent via a durable power of attorney?

PHI regarding a decedent is protected by HIPAA. a disclosure for the purpose you describe would, therefore, require an authorization. You should look to state law to determine who can act as a personal representative of the decedent to execute the authorization.