Can Disk Utility and Disk Warrior be used on a Fusion volume containing Mac OS X
Both Disk Warrior and Disk Utility will work on a .vmdk mounted volume using the VMDKMounter.app IF the .vmdk is not damaged.

I created a new .vmdk, recopied the drive image and both Disk Warrior 4.4 and Disk Utility worked fine.

It appears that if the .vmdk becomes damaged somehow, the normal tools I use will not work.

Keeping good backups appears to be even more important when you add Virtual Machines to the mix.