Like others, I think it's not totally necessary with tarots - especially ones that follow the RW closely. Super abstract or oracle decks - almost a must, especially oracle. It's funny you mention this because I've been wanting to do a book for a deck too. And I don't want to do the art. Odder still because I'm a artist/graphic designer yet I don't want to - I want to do the book. Maybe because it's a novelty sort of deck I have in mind and I'm wanting it to be humourous as well as a little educational, so I have a pretty good vision of what I want. Just too much stuff on my plate to do it all.
witchofglass - I might hit you up for editing too if I ever get this started. Was thinking last night of contacting another designer/artist friend from high school and seeing if he's at all interested in illustrating.
Kat I think it's great that you want to hook up with an artist for a collaboration. Lots of people can't or don't want to do both. I hope you get some interest