Until you will fix the compatibility with Greasemonkey, here is my advice about what to do in mozilla, to get it work.
1. Uninstall (remove) all userscripts, including Greasemonkey.
2. Restart browser.
3. Install version 1.15 of Greasemonkey
https://addons.mozilla.org/pl/firefox/addon/greasemonkey/versions/?page=1#version-1.15
4. After restarting browser, go to Tools/Add-ons, then click on Settings icon (near the search bar in the top-right corner), and uncheck "Update Add-ons automatically". This prevents Greasemonkey to update itself to version 2.0.
5. Restart Browser, install Dio Tools, and then restart mozilla again. Now, it should work!
This worked for me! Great job Diony, I love this tool, is part of the game for me: )
Good luck!