Here's the thing between Succor and Stoneskin II. Succor only lasts 30 seconds but it's protection is vastly superior, especially with a properly geared Scholar (i.e. crit-stacked like a boss). Further, Succor heals as it protects. Stoneskin II doesn't heal and only offers a fixed level of protection depending on I want to say the conjurer's HP, though it could be the target's HP. Either way, it's a fixed amount. Stoneskin alone barely lasts a few seconds once combat starts, and that's with the boosting trait. Stoneskin II can't be reapplied during combat but Succor can be spammed all day long. Scholar has a marked advantage here, why would any Scholar waste a cross-class slot on Stoneskin II? I know I wouldn't.