Machine powers off and cooling system works normally
Machine powers off and cooling system works normally
When lowering TDP doesn't resolve the problem in D4, I'd consider both reducing TDP and adjusting settings while capping frame rate around 60 fps. If that still doesn't help, it might be a software-related issue—given your RTX 3080 could only draw around 200W at its peak, it's likely well under any limits you'd set. If the fix works and you prefer not to replace your power supply, tweaking Diablo 4’s 3D settings in the Nvidia Control Panel can help prioritize efficiency.
You're checking performance at 75% power with low quality settings and a 60 fps cap. It's unclear how long to run it to confirm results, and you're wondering if there might be software problems. After a clean PC reset and reinstalling Battle.net and Diablo, the issue could stem from driver conflicts, resource leaks, or outdated drivers.
This would further reduce the chance of a software problem, so if it isn't my first guess then I'd assume Diablo 4 is simply conflicting with your setup. Such a situation is improbable, but we'd be relying on weak evidence after all the tests we've done.