Is oops of kernel tainted by staging device less likely to be investigated? I understand that kernels tainted by binary modules are less likely to be investigated by kernel maintainers. However what is the policy if kernel is tained by staging driver (if the staging driver is broken it is still problem in kernel hence some Linux developer might be interested). Does anyone knows the current policy (most resources I found simply states to "uninstall the binary ATI/NVidia drivers" - I guess it is the most popular way of tainting the kernel).

Yes; it's likely to be ignored by most kernel developers. If the problem is reproduceable, remove the module that causes the kernel to be tainted and see if you still get the kernel panic. If you do, you're more likely to get interest from people. If you don't, contact the maintainer of that module and give him the relevant information. If it's difficult to reproduce, also just contact the maintainer of the module.

To find out who has been working on that module, you can look at the commit history.