I used to use Stone I against the slimes on Amon in Syrcus Tower, to help slow them down so the group had more time to kill them. I haven't felt a pressing need to use Stone I in Heavensward content, though. I just use it when I'm synced.

You have to be kind of careful about what you use that heavy on, anyway. Really obscure example, but that guildhest with the lily that throws poison everywhere. If you spam stone on the enemies, they will crawl out of the poison clouds more slowly. This might encourage the tank and melee to fight in the cloud. Nothing that can't be healed through, but it can do more harm than good if the healer doesn't anticipate this.