The GDS Service Standards for GOV.UK services calls these “Content Designers”. But we’re talking about the same thing.
Loads of Content Designers / UX Writers produce less-than-ideal content, though. Like any role, experience is important.
And above all, iteration based on user research / data insights is key. Don’t rely on intuition.
I use http://www.hemingwayapp.com a lot. It’s a great tool to improve readability.