MadCap is a good option in a field that doesn't have many outstanding alternatives

We use MadCap for all of our technical writing needs. This includes product guides and software user manuals. The software addresses the need of hosting our documentation as well as allowing us to share documents with peers for review before publication. The software also (attempts) to address issues of single-source documentation through features such as Snippets and Variables, though this is often a pain point.

The software does allow for "conditioning" of certain content within a single document, allowing you to publish only certain parts of a document depending on where you're publishing it. For example, an Introduction paragraph might be necessary for learning materials but not in-product help. Conditioning allows for that. This is a feature we put to work quite often within our organization.