More DPS options is good. Outside raid scenarios I'm using my attack spells a lot.

Very curious how a Stone III would fit in, since Stone II is already the spammy single target nuke. My guess would be that Stone III debuffs the target to earth damage.

I doubt it will be a debuff that's useful to the party. That seems more fitting for DPS jobs to apply. WHM offers plenty of support with healer-related tools.