I stumbled across a way that makes it more enjoyable to play Grim Dawn with a controller, by using Steam Input and the options it provides. All you need is Steam and Grim Dawn on either Steam or GoG (added as a non steam game in the Steam library)
When you follow this guide, the camera zoom (not rotation) will be locked when the (mouse) cursor is not showing in game. And when the cursor is showing on screen you can move the right analog stick up and down. That enables you to browse inventory, map, questlog, etc. without a problem.
I have created the guide on Steam, I hope I don’t get in trouble for posting links to another website. Seems kinda daft to re-create it here, but will do it if have to.
Have fun!