I'm reasonably sure that using dragon stones doesn't count as wearing armor in terms of absorption, making dragon stones terrible. You take 25% extra damage for each piece of armor you're NOT wearing, so wearing no armor for the dragon stones means you take 100% extra damage (it's not multiplicative), basically like wearing the calamity ring. I'm pretty sure this is the case by comparing full dragon form to full master's attire, the weakest armor in the game. I took way more damage in dragon form. Needs proper testing.