Current fix for Warrior is not using Warrior Skills?

[Gamemako]

PLD uses Rampart and then gains Stone Skin. Stone Skin absorbs 20% more damage than without Rampart = 20% stronger = 'Extension'. Can be done every 90s vs every 120s (Thrill of Battle).

25%. 1/0.8=1.25. Also 20s duration.

PLD uses Sentinel and then gains Stone Skin. Stone Skin absorbs 40% more damage than without Sentinel = 40% stronger = 'Extension'. Can be done every 180s vs every 120s (Thrill of Battle).

66.67%.

no boss currently has such a predictable + slow + large wind up hit to make this a viable option.

Not necessarily. A PLD, however, can hit Stoneskin without taking healer MP, so that typically makes much more sense than losing healing for a duration to drop an inefficient shield.