@peaches
Thank you for your clear explanation .

@DarkLordCthulhu
As a WHM, combat Stone Skin is used sparingly only, such as for Megaflare, T7 in between 2nd phase add spawns, Ravensbeak, 5x Bahamut Claw, Death Sentence, Titan Ex 3 stack Mountain Buster etc, AKA attacks that has a chance of outright killing your tank/raid team.
Other than that, any other mitigation by use of Stone Skin is MP inefficient, why SS when I can heal the tank back up to full easily? SS costs 266 MP, same as a Cure II, double of Cure I, sure it makes you feel like a badass when you see the mountain buster barely nudge the tank's HP bar, but I can also feel like a badass when the tank's HP drop to 60~70%, then go back up immediately within 0.5 second because I timed my heal nicely .