Given how easily RDM can cap stoneskin these days (Theoretically it can be capped naked outside of abyssea, nevermind inside) these become the best item in the slot by far, assuming they work the same way as Mufflers/Gorget.
More Stoneskin gear means more RDM solo efforts and PLD/RDM. It will be interesting to see how much all the Stoneskin gear together adds to damage absorbed.