I only have three of her decks, but of the ones I have, I always felt like they were all quite distinct from one another, so at this point I'm not raising my eyebrows over Alana Fairchild putting out so many decks. I believe that perhaps it just comes very naturally to her, as her decks seem deeply inspired rather than churned out in a mechanical way.
I think the Isis Oracle is especially unlike any other deck I've had in my opinion... If I had unlimited funds, I'd buy every single one of her decks, even if just out of curiosity -- and well, maybe only then could I form a more certain opinion on the matter!
The Crystal Mandala deck looks interesting. I wonder how good of a deck/guidebook it would be by itself if you didn't own her related books ('Crystal Angels 444', 'Crystal Masters 333' and 'Crystal Goddesses 888')? No way do I plan on buying all those, I think.