This thread!

I only cast stone skin in t9 and only once during phase 1 during the first iron chariot and then twice in phase two while waiting for the golems to spawn.

Stoneskin interrupts your combo so unless you are doing it for fun it's pretty pointless.

Skill speed and crit are equal for PLD and I'd put SS over crit for WARs.

WARs benefit from IR and Zerk and SS helps fit attacks. Any WAR using ruby accessories can appreciate the extra SS.