One method of approach that might work faster is to "limit" the types of files that DR3 is attempting to scavenge and recover.
For example, I had a partition on an external hard drive go bad on me -- simply wouldn't mount, no matter what I tried. The other partitions weren't important, but this one was -- it contained all my stored mp3 files, and I didn't have a backup for many of them.
My solution was to completely re-initialize the drive and then "attack it" with DR. Since I couldn't get the damaged partition to mount on its own, the only way to get the drive "visible" to DR was to re-initialize it. Yes, this destroys the existing partitions, but remember -- partitions are a creature of the drive directory and re-initializing in and of itself doesn't "touch" the data that is lying on the drive's sectors, even if you don't have a good partition to "show the pathways" to that data.
Once re-initialized, I was able to mount the [now, apparently empty] drive in the Finder, then go after it with DR.
I set up DR to look for only mp3 files, and turned it loose.
It did take me three tries, but on the third time I got the majority of the mp3 files back (although all folder hierarchies were lost). But it worked.
I believe by limiting what you're looking for, DR may be able to complete its work in less time. Might be worth a try.
