Hold on there a moment. There's a difference between being decent (The Schroeder's Valkyries and Fairy Tales) and being OP. Monsters like Geh, Kyutora, and Gigas fall into the OP category.
Dartz is a weird one because not only are his cards blatantly OP, but his cards from the anime either don't exist in the actual TCG or have totally different effects if they do exist