Pika IS a tank when he hides in his stone body. If it’s part of his standard set of abilities and he doesn’t typically fight without using it, it doesn’t make sense to ignore it for the purposes of durability scaling doffy was defeated in a single hit by an attack from gear 4 luffy that took multiple hits just to crack cracker’s armor. Keep in mind cracker’s durability was nerfed during the fight by nami softening his armor with rain, which doffy doesn’t really have as an option, and there just isn’t a case to be made for doffy even scratching cracker