I had the same problem until I enabled it.
I had disabled it in 7.5 for latency issues but word is the revamp in Cpro8 doesn’t actually exhibit the same latency trouble even if it is showing higher values in the VST Sound System device setup menu.
Haven’t got around to testing this myself yet so I can’t say for certain.
I’m having the same issue, but I’m on Windows 7. I have also had a crash trying to render Superior Drummer in place with multiple outputs enabled. Seems like I have to restart to get the project to open again. I have asio guard enabled set to max.
You may want to try and Save as a new project in Cubase 8. For example, I opened up a project with the name “Project Name”, as soon as it was open in C8 I saved as “Project Name1” and the project now opens and closes with no problems.