Stoneskin interrupts your combo and kills your DPS! I do cast it a few times in t9 but never in t6-8.

A more useful tip would be to swap into Sword oath during T6-8 when you have extra CDs available. Sword Oath > Rampart during T7 is a common one. No extra damage taken and you don't need to save it for anything.

PLD TP is really never an issue, if you are low so is your MNK/DRG/BRD and songs are incoming.