Question:

Will the Vigor2910 router running the latest firmware (3.2.0 and above) support multiple USB hard-drives as well as a printer when using a USB hub?

Answer:

The 2910 router will only support one USB Flash drive with the current firmware. It will be accessible via FTP for file storage.

You can use these USB devices with Vigor2910 at the same time, by the use of a USB Hub. Ensure the USB Hub has its own power supply to avoid insufficient power being available for all the USB devices.
See also “USB disk quick settings“.