Ref this thread too - R/D/T questions - #23 by ironboundtome
As a preemptive action to answer for my group; what would be the scaling up of damage given the additional potential impacts when Target is changed from Ind to group? In particular I am thinking of what happens in the 3rd example below, but also generally.
I am thinking of the implications of "Arc Fiery Ribbons" which applies the group target to create the fan of effect, but cannot find a similar spell which demonstrates the difference when a spell like Crystal Dart is scaled up to a group casting.
I also think that it is totally subjective to the spell description (typically ysmv); which leans me toward having many options:
1 - it might enable a wide arc (like AoFR above) of effect. Plausible and highly referable. This might make avoiding it far harder, make it better for mass combat usage, but also limit the applications when allies are in mixed melee.
2 - it might enable multi-targeting all members of a group auto-magically (like casting a dart at each in a fighting formation). Sympathetic to the meaning of Group, with one "hit" per hostile group member. To me this sounds very appropriate, but also limits greatly the application.
3 - it might enable multiple hits on the same target. This is where the trouble starts. I'm not adverse to saying that group basically cannot be used to generate multiple concurrent hits on the same target (as the one target is not a group), and having the caster either multi-cast or consider the projectiles as one "impact".
Expansion on the benefits of option 3:
3a - increased damage. How much?
3b - increased benefit to Finesse rolls for targeting, such as spells like Vil's Sling, which is targeted with Finesse. This makes sense, as you're likely to hit with one of the impacts, but you'd have to consider collateral affects too with all the misses.
3c - at what point does it become almost a rain of impacts, which is impossible to avoid - and deadly given the other effects.
Apologies in advance for the "munchkin-ism" of this - I'm seeking to prep my answers beyond just "nope, not allowed".