Hi @Gajack, the short answer is that the W3af add-on is not currently up to date with the latest versions. We have an older repo here but it's in the old style and needs to be converted from a "plugin" to a "gem": https://github.com/dradis/dradis-w3af
We have ~20 or so add-ons, and ideally we'd like to convert them all, but we had to start somewhere. We started with those that would make a bigger impact to our users (the usual suspects like Nmap, Nessus, Qualys, Nexpose, etc).
At this point, we still haven't migrated the W3af plugin because not a lot of people seem to be using Dradis and W3af (possibly a catch-22 situation).
Would you be interested in helping us get the W3af add-on updated? We'd need some current sample results files to exercise the parser and the unit tests. And if you have Ruby chops, we could do an initial restructuring of the repo's code to make sure it loads into the framework, and so you could contribute to the actual parser implementation. Let me know what you think!