I help friends garuda farm in pugs and occasionally get terrible healers that panic when the adds come out. I'll generally pop a cd and start spamming stoneskin. It has saved my bacon a few times when one healer was trying to manage two tanks and HG wasn't available.

But yeah, pld's cross class selection is pretty awful but stoneskin is probably the second most important ability you can equip (after foresight) so even if PLD had a better selection, stoneskin is staying for a while.