Hi,
Thank you for sharing the issue and I am very sorry about the experience!
From your description, I believe the Point Cloud should be visible after using Graphic Override. Did you try to
Rebuild & Regenerate
(View > Refresh > holding Alt to show Rebuild & Regenerate)? This should help to apply the transparency into the selected elements.
Let me know if this helps!
Best regards,
Minh
Minh Nguyen
Technical Support Engineer
GRAPHISOFT