Gustorn said... Could you try installing the adobe-source-han-sans-otc-fonts package, restarting FF and check if it works?Doing this install and rebooting did the trick. (note: I rebooted my entire computer out of habit from having just set it up, so if simply restarting FF doesn't work try a full reboot.)
EDIT: also, try following the steps here: Font Troubleshooting
Thanks for the help guys!