If writing (or getting people to write) user documentation is hard, perhaps you can put together good video tutorials on how to use many/most/all of the features in each module. You can even get developers to actually do the video demonstrations, because it gives them a chance to show off their cool new accomplishments. You can probably get people to do replacement narration as well, both for developers who don't do a good job narrating (language issues, accents, mush-mouth mumblers, etc.) and for alternative languages.
Put those videos up on Youtube or Vimeo, perhaps even annotate them with links to the official docs (such as they may be), with notes about features not demonstrated in that video, or with links to related training videos.
Then you can point to those videos not just for training materials, but as marketing/demo items.