Hello,
I am afraid, it is not.
Apologize, It seems you have not read the above article provided properly.
It states, "For a list of Class IDs you can click here." and this link directs to
http://msdn.microsoft.com/en-us/library/windows/hardware/ff553426%28v=vs.85%29.aspx
However, You need to exclude the Device ID or Class ID of the webcam (internal / external). You may use the DevViewer.exe tool from the SEP Manager setup CD (Under Tools folder) to copy those IDs to clipboard.
However, the important point is that you'll confront with things like that in the future. If all you want to do is block all USB storage, I'd suggest you to create a new Device ID under Policy Components -> Hardware Devices with this ID: USBSTOR*
You can use wild cards like * (star) in those fields. And all usb storage device IDs start with USBSTOR tag. That way you will not need to block whole USB class which will always lead problems.
In addition, in the future you'll see that some USB hard drives do not go under USB class and do not get blocked. So you'll have to use this method anyway.
How Symantec Endpoint Protection Device Control processes Windows device GUIDs and device IDs.
http://www.symantec.com/docs/HOWTO60964
DevViewer - a tool for finding hardware device ID for Device Blocking in Symantec Endpoint Protection
http://www.symantec.com/docs/TECH103401
Hope that helps!!