When should WHM use Stoneskin I?

[Risvertasashi]

Stoneskin just the tank for trash pulls (especially those larger ones in SV/DD/AV). For final bosses I would just stoneskin everyone, negates some party damage just in-case tank doesn't get that aggro right away.

I recommend stoneskinning everyone in the party. If a DPS pulls, eats an avoidable, or something else unplanned happens, this gives healers a bit more breathing room.

At level 50, swiftcast + stoneskin 2 makes this very easy to do as the group is running to the next pull.