Discord overlay doesn’t pop-up but instead when I use the key-bind it freezes my cursor.
I have a remedy for this;
When you first open Blizzard (before launching Overwatch) click the “Play” button then quickly click back to discord.
Discord should be on top of everything else, including the Blizzard app, before the game actually opens.
When in the game (before you start playing), give it a moment to load, then the overlay thing should appear after a few seconds. Test it first to make sure it will open and close without freezing your mouse.
This works for me but may not work for everyone.