[Feat Concept] Elemental Burst: Please evaluate

[Shhalahr Windrider]

When you make a critical hit with a spell attack that deals acid, cold, fire, lightning, or thunder damage, a wave of elemental energy bursts out. This wave deals half the damage done to the original target to every character within 10 feet of the creature struck by the spell. This damage is of the same type dealt to the original target. If the attack was a melee attack, the caster is not affected by the wave of energy.

[hr]

This is a first draft. Bit more of an initial concept than anything final.

What do you think? Too powerful? Too weak? What could be done better?

[JNAProductions]

Too weak. It'll be nice, if it procs when you make an attack roll spell while enemies are closely clustered together.

But what are the odds of that happening? Most spells rely on saves, not attack rolls, so they CAN'T proc it, and the few that do, have a mere 1/20 chance of doing that, and enemies won't ALWAYS be clustered. And allies will be in there too sometimes.

About the only thing it might work on is Cantrips, and while 11 points of damage in a 10' burst is nice, it's too unreliable, ESPECIALLY for a feat.

What I'd do is simply allow you to do this:

Elemental Burst
-When you make an attack with a cantrip that does acid, cold, fire, lightning, or thunder damage, you may choose to instead make it a burst. Select a spot within range-all creatures within 10' of that point (excluding you, if it's a melee-range cantrip) must make a Dexterity save against your spell DC or take half of your cantrip's damage, or one-fourth on a successful save. (Some cantrips may require other types of saves-talk to your DM about this.)
-When you make an attack with a cantrip that does acid, cold, fire, lightning, or thunder damageand choose not to burst it, you may add one point of damage per die.
-You learn one single offensive cantrip of your choice that does acid, cold, fire, lightning, or thunder damage.

[Shhalahr Windrider]

That sounds good, I think.