Ok I finally got this working on steam deck with auto launch.
In properties, general, set launch option to x64, then add
WINEDLLOVERRIDES=“winmm=n,b” %command%
to the text box.
Under compatibility, check the box and select Proton 7.0-6 (this also stops the memory leak)
In desktop mode you do the installation as stated in the first post.
Installing the VC++ redistributable using protontricks:
Install/Launch protontricks
Select Grim Dawn and click ok
Select default wine prefix, ok
Select install a windows DLL or component, ok
Select vcrun2022, with the title “Visual C++ 2015-2022 Libraries”
The window will disappear, but it’s working in the background. You may get some errors saying the checksum was incorrect, just keep retrying until eventually it completes. You’ll know it’s finished when it takes you back to the protontricks window.
Doing this my game runs flawlessly and has no visual glitches. I do have my settings turned down to save battery life though.