In my experience, documentation becomes outdated and fragmented very fast. If I had a say, I would make a rule that every employee should maintain only up to 10 wiki single-pages for their most important products, components or processes. At the top I would require a system overview diagram. And no details, only high-level concepts, keywords, pointers, links and contacts.
Can you show us "definition of done" for your process of closing a ticket? It looks like the "* [ ] update relevant documentation and list link to the documentation changeset" step is missed.
