Yes, that method has worked for me, but it has some serious limitations.|
One of them is that the backup will always be of the same size as the full card size, as even unused parts of the card will be stored in the backup. So a 32GB card will have a 32GB backup file, and will take a very long time both to backup and to restore (if you ever need to).
Another limitation is that such a backup can only be restored with certainty to exactly the same card, since card size varies between brands and models. Two different 8GB cards (for example) do not have exactly the same size. The manufacturer's spec only means that the card has at least 8,000,000,000 bytes. But nearly all brands and models differ between each other in the precise size. There may even be differencies between different units of the same brand and model, though they are more likely to match up. But if even a single byte is missing then Win32 Disk Imager will fail to restore a backup...
Best regards: dlanor