Doesn't PLD already have to do that as it lacks personal cooldowns out of the 4 tanks? As well as the other tanks to some degree. So that notion seems unnecessary, especially since they've removed a lot of mitigation skills from Stormblood and previous xpacs so tanks universally have fewer to each job they already ration out. Each "spammy" mitigation they do have even comes with a downside or limitation inherently: Sheltron uses Oath gauge, limiting you to 2 in a row at a time; Heart of Stone is the weakest as far as protection; The Blackest Night costs 3000 mp, which you only can pull of 3 ideally before bottoming out your MP (capped at 10000); and is a WAR uses Raw Intuition, it costs a usage of Nascent Flash and to use Nascent Flash costs a usage of Raw Intuition.