My understanding is that the most important part of the Swarm's public API are the Swarm class and various ShrinkWrap *Archive classes defined in the respective fractions (e.g. JAXRSArchive or WARArchive). (And also the Config API, but that has documentation generated automatically.)
Given that these classes will be encountered by a vast majority of Swarm users, they really should have a good amount of Javadoc. The Swarm class has very little, the archive classes almost nothing.