Dino toughness is literally just Kaido's toughness, thats why Ancient Zoans are called "Ryu Ryu no Mi", which means Dragon Dragon fruit. Making Kaido feel pain isn't a big deal for today's standards, if we take strong characters into consideration. Even Momonosuke did it, with a bite.
Also, it doesn't mean all the Dinosaurs have the same durability and endurance, the strength of the owner of the Devil Fruit is still something to be taken into consideration. Queen, a Cyborg, is someone much tougher than Page One for example, Oda literally made Marco hit him alongside King with flames on his back
The only one who is factually above them is the Lunarians with their flames active on their backs