Destruction Domain: Clerics who find everything a battlefield.

[sandmote]

The Aura CAN add +30 damage... If you have at least six allies, and all of them hit with at least one attack before your next turn. Which doesn't feel super likely to me, in most normal-sized games.

I dunno, I feel like it's something I'd almost never use due to action economy. If your table rolls differently, it can work for you, but to me? Not a very appealing feature.

I again note that the bit of your suggestion I left out was the one making it easier to apply the effect again for a consecutive round (ie. adding on another +30 damage). It does also apply to spells and non-attack damage.

Admittedly it probably doesn't scale great given you'll eventually be dealing an average of 26 damage per turn with Toll the Dead. On the other hand its a full caster class and this happens starting at 17th level, so I'm leaving it for now.

Ex: two the members of the team have shatter and use it at once to try to kill three targets close to each other: on their own they will dea a total of +30 damage(+10 to each target) without you needing 6 allies.

This would be broken and I've attempted to remove it from the latest version of the feature. The effect currently should apply to a single damage roll. For further commentary on this, please see discussion on the Draconic Bloodline Sorcerer's Elemental Affinity feature.