Your posting describes members who open the portal only when something has gone wrong with a claim or a bill. That has been my user for the past four years at Northstar Health Plans, and designing for people who arrive worried and in a hurry is the work I most want to keep doing.
The clearest example is our claims status page. Members called member services because they could not tell whether a claim was processing, denied or waiting on them. I ran 14 moderated sessions, found that most confusion came from adjudication terms we had copied straight from the claims system, and rebuilt the page around one question: do I need to do anything? Claims calls dropped 18% the following quarter. The case study on my site shows the two directions we tested and dropped along the way.
I also look after the portal's Figma library, which now has 64 components with high-contrast variants, and I led a WCAG 2.2 AA audit with our front-end engineers that closed 97 of 112 issues before release. Before Northstar I spent three years at an agency, where I learned to test quickly and explain findings to clients who had not watched the sessions.
I would be glad to walk your team through the claims project or any part of the portfolio. I am available most afternoons and can come to Minnetonka.