Keep in mind Yoshida wanted to remove Stoneskin when they made the transition from 1.0 to 2.0. I sort of see why, and while heal output does seem to outstrip Stoneskin in the middle of a fight it's still fairly useful (granted, I'm a PLD, and I can get out more Stoneskins than I can Clemencies with my MP bar).

This said, I don't think you guys want Stoneskin II made available to other healers. You'd be giving up one of your cross class slots to get it (remember that Stoneskin II is a separate skill).