In general, it’s probably reasonable to have a per-transaction fee and a percentage fee for this sort of thing. Because of batching of transactions, it doesn’t really line up with credit card processing charges but presumably Patreon has some costs that are effectively per-transaction: infrastructure, dispute resolution, credit card transactions (loosely), etc.
I have no opinion if these new fees are “fair” ones whatever that means. They certainly bias against small donations though. It’s not even so much who pays the fees. I see the psychological elements. But I assume a lot of creators (and patrons) would be just as upset if the creators were now only seeing 62 cents out of every dollar with the rest going to “hidden” fees.