As it turns out, Disk Utility WILL create an HFS standard disk image from an external drive. Mount and highlight the HFS drive you want to create an image from. Under "File", "New", "Disk Image From (Select a Device)..." This produces a perfectly functional HFS disk image.

Presumably, Disk Utility must be able to mount the disk in question, so if Apple ever completely drops HFS, I would presume the option will no longer be possible in Disk Utility. Is this just "dd" via Disk Utility, or is Disk Utility really something helpful?