WordPress and several other pieces of web software written in PHP are notorious for using old and broken algorithms for securing passwords. If you are using a PHP version of 5.5 or newer, you should get okay security by default. However, even phpass’ developers recommend not using their software if you can use PHP 5.5 or newer. I strongly suggest installing and enabling the PHP Native password hash plugin, especially if your WordPress install was ever run on any of the PHP 5 family. The plugin’s two most significant advantages are it actually gets updated to include new, more robust algorithms, and it automatically migrates passwords to the newer algorithms on login.