This can be fixed without root, as you can give Sentio Desktop permissions to edit the display settings.
HOWEVER, I don't see anyway to turn off the display when plugged into the adapter and keep running the same.
This is more of a long-term problem. Having the screen on for extended period of time will cause heat issues, not to mention wear on the screen.
Is there any kind of way to turn off the phone's display when hooked in, akin to closing the lid on a Mac when hooked to a monitor (without root preferably)?