It would be nice to at least mention in our docs that arcanist may require patches that could be found in this thread.
But forking it is definitely more user-friendly.
FWIW, I had some success just using the master branch from GitHub - phacility/arcanist: Command line interface for Phabricator
I did have to uninstall the Ubuntu arcanist package though, since for some reason even the locally checked out clone seemed to pick up some code from there.