Just about all XML editors I’ve seen presume that you’re working in something that looks like a Word document. But what I really want is a bunch of structured fields containing text.
Think of writing 50 manpages: you don’t really want to have each manpage be a new, unstructured document. You want to ensure that all fields are in the correct order and that none are left out, though the content of each field is arbitrary. You probably want some styling for text, to indicate command names and the like.
In the past, I’ve used a spreadsheet for this sort of work, but spreadsheets are awful for inputting large blobs of text—worse than database text fields by far.
(Many) extra points if it runs on Linux, Mac, or in a browser.