JSX is very close to HTML. Maybe the issue is expecting designers who have zero dev skills to build front ends in a time of responsive design and rich JS interfaces. You wouldn't hire a print designer with no Photoshop experience to design a site, and you shouldn't hire a graphic designer with no web dev skills to build front ends. If you're team is really well formed, you might have an experienced graphic designer, a UX expert, and a front end developer who does the actual building as well as making day-to-day design decisions. The design/interface experts would work at a higher level of creating an overarching design language and UX guidelines.