Hi @taqie,
I'm in the process of refactoring our statuses to be much better, and it's on our roadmap to be in the v3.3 release next month.
The current api/v3/users/status service is a POST and requires a request payload that is a list of user IDs you'd like the status for. For example, providing a requset payload of ["1zkzkhh357b4bejephjz5u8daw", "3bq1shta93yztg3i6aiu1tzi5h", "5iz3prremfgx5goqzpfjbsfd9e"] will get you the statuses for these three users returned as JSON, specifying "online", "away" or "offline" for each user.