Great for your Stoneskin macro as WHM or SMN. With capped unmerited enhancing magic on WHM (230), you need 104 MND total to max Stoneskin damage absorbed at 350 damage. SMN/WHM needs lots of +MND but Stoneskin is far better than Earthen Ward when you equip right (for yourself anyways ^^)
To Ascot:
If you need Stoneskin/Earthen Ward at all...it's probably not gonna last 5 minutes, let alone 15.
To Bekisa:
Rate up for informational post! ^^
To Ascot: /sch or SCH you can accession + Stoneskin which is superior to Earthen Ward. SS is also much better than EW for the fact that it doesn't require an avatar to cast it...
to Bekisa, Stoneskin isn't that better than earthen ward, from stoneskin you get 50 more damage absorbed, but you really need loads of mnd to reach cap. Alsot stoneskin stay up for 5 minutes, earthen ward for 15 minutes.