The cards aren't standard size. They are tiny - 2.5" x 1 5/8"
That is a standard size. It is one of the two most common sizes for cards in board games. It may very well be THE most common size for cards in German board games.
The fate deck is being shuffled infuriatingly often, but I don't really think it will harm this deck more than the players' Action decks which are also used a lot.
However the cards are of high quality and even wear and tear won't matter much in the long run.
(From a player who had seen some ugly card decks in Civilization over the years, and there it DOES matter whether the disasters are recognisable or not, but that has never prevented us from playing).