No, PLD stoneskin is just as bad even at lower levels which deprives them from flash use. Second, it's not a real cooldown. The long cast time also means they can misjudge a busting cast bar mechanic that needed an actual cooldown and end up killing themselves because they didn't use the right skill.

PLD stoneskin utility is only there is nothing else to do, like the boss is away like Thordan EX and Ultimate End to help someone weak. Otherwise the PLD should be hitting the boss to keep hate and keep DPS going. Even extended Clemency use is subpar with it's longer cast time that a healer can restore faster. You only get 2 casts of that skill anyway with it's huge MP cost.