The only projects I've backed (not tarot related) have expressed a clear set of obtainable goals and seemed really well organized. Their need for funding was specifically targeted towards bringing the product into production and getting specific things to the people who've pledged certain amounts of money. As their project grew (successful), they added stretch goals, to encourage people to continue adding their support.
I'm a bit leery of funding something as vague as an art project of any kind, and I guess I don't understand why someone creating a tarot deck wouldn't have already mapped out the entire deck in terms of style and format, much less each card
Do people really expect to get funded while they're still working out their overall project? Sure, I get it, people are passionate about their art, and the technical requirements of bringing a deck into production are likely a lot of work, but I don't see how people can ask for financial support without reasonably well thought out third and fourth rough drafts for each card, and a clear plan for the deck as a whole. Even if those rough drafts aren't the final product, at least their backers could see what they're aiming for.
I guess for me, it's a business decision, and if the project doesn't seem well thought out and organized, I guess I'd be reluctant to get involved just because somebody's got an idea about some pretty pictures they might someday choose to share in a tarot deck they haven't yet envisioned in its entirety.