I'm a new paly and have thought about this alot. Stoneskin is a great skill for end game. My FCs ot is a warrior who currently caps around 8-9k hp. We all know warriors have mitigation issues and probably always will else what's the point of being a paladin? During coil the mt and ot have moments where they need to back up / wait for a small period of time. If the mt is a paly then casting stoneskin on a warrior would help a grap ton. Most end game warriors are 8-10k hp it seems to me that casting SK on them helps them mitigate 8-10k dmg. In my book that's huge not only in a oh shit situation, but a helping the healers conserve mana one.