Here's the arrangement contemplated: The employer will provide and pay for 75% of premiums for a high deductible medical insurance policy for all employees except the highly compensated and 5% shareholders, who will not be included in the HRA. The employer will also pay for a portion of deductible expenses for those covered employees by paying the provider directly for covered expenses up to a specified dollar amount.

Since the highly compensated and 5% shareholders aren't covered by the HRA, the employer wants to pay 100% of their premiums.

Does this violate any nondiscrimination rules or ERISA?

nondiscrimination rules only apply to cafeteria arrangements and 105(h) self funded medical plans.

your scenario does not state that the payments are through a cafeteria plan and if paid directly by the employer would not violate any discrimination rules.