Have a conversation with your direct manager to make them aware of your concern and frustration. They may not understand the healthcare impact or failed to consider it during the raise process. This may due to a lack of knowledge or they may be juggling so much that they meant to check into it and just failed to get to it in time.
I doubt that you will change the policy with your concerns but you can help your direct manager see the impact, demoralizing, of a raise to right above those certain thresholds. Also, bring this up in your next few annual reviews, in a polite but frustrated manner, and see if you can score a slight bump or two that will help offset it in the long run.