These problems with DX:HR are due to:
a bug in DX:HR, which is easy to correct via registry settings.
an nVidia driver issue when using switchable graphics, which is easily corrected in the nVidia driver settings.
1. Registry Settings
Two registry fixes are required.
HKEY_CURRENT_USER\Software\Eidos\Deus Ex: HRDC\AllowJobStealing to
for NVIDIA owners - set registry key
HKEY_CURRENT_USER\Software\Eidos\Deus Ex: HRDC\Graphics\AtiForceFetch4 to
2. nVidia driver settings
If you are playing on a laptop with nVidia switchable graphics, i.e. switchable Intel integrated/nVidia discrete graphics cards, you will need to apply this fix.
The issue is that the nVidia driver determines when to switch to the high-performance nVidia graphics card based on the name of the program executable being run.
DXHR.exe is on the list of "programs requiring high-performance graphics", but
DXHRML.exe (the Missing Link) and
DXHRDC.exe (Director's Cut) are not on this list.
The solution is to manually tell the nVidia driver that you would like
DXHRDC.exe to be run using the high-performance graphics card.
Open the nVidia Control Panel.
Select a Task, open the
3D Settings >
Manage 3D Settings pane.
Add button to add a new program. Find your DXHR executable - mine is located at
D:\Steam\steamapps\common\Deus Ex Human Revolution Director's Cut\DXHRDC.exe.
Tell the nVidia driver that you always want to run
DXHRDC.exe using the
High-performance nVidia processor.
After applying these fixes, I am able to play the Director's Cut at the same graphics settings as the original Deus Ex: HR - that is, full-screen 1920×1200 at high graphics settings.