It is as bad as it seems (probably worse)
This is the only case, and even Electric Arc does it better, while spending less resources.
Most spells that do nothing but damage tend to scale 2d6/level1, half of it is 1d6. So 3.5 damage if you hit, 0 if you miss.
Comparison with Scorching Ray
Scorching Ray does exactly twice the damage for one less action2, or twice the damage to one more target for the same number of actions, without ever spending a feat.
Comparison with Electric Arc
Spells with basic saves deal half damage even if the enemy saves. To simplify calculation, say they do 50% more damage (actually, it is even more).
So now we can compare that spell in your highest slot, modified by Split Shot with Electric Arc. The latter scales with 1d4/level, which is 3.75 after the 50% increase. It wins easily, even when we ignore the extra damage from the spellcasting ability modifier, the fewer actions, and the fact that you don't have to spend your highest slot.
The slot + Split Shot can still be better in three cases: the enemy is further than 30 feet away, or is immune / resistant to electricity, or you do not have Electric Arc.
- The first can usually be fixed by Reach Spell, which is not only more versatile than Split Shot, but also of a lower level
- The second is rare, more than offset by the fact that good spells with an attack roll are even rarer
- You can get Electric Arc for a General and an Ancestry feat3 (Adopted Ancestry + Adapted Cantrip)
Also, if one of the enemies has so few HP, it might even die if it saves, while an attack spell does nothing on a miss.
Homebrew fix 1
Just replace "two" with "three" in the feat description:
If your next action is to Cast a Spell without a duration that requires an attack roll against a single target and has no effect beyond dealing damage, you roll a single attack roll and compare the result to the AC of three targets within the spell's range
I still would not take it probably, but now it has a chance to be better than a common cantrip.
Homebrew fix 2
Just remove "only half"in the feat description:
The spell deals its usual damage to each target.
Still worse than Scorching Ray, while more costly (more actions, costs a feat).4
- if you find a spell with higher damage that works with Split Shot, let me know in the comments, and I will run the numbers
- assuming the base spell takes 2 actions, as most spells do
- you should, it is that good, and I (like most guides) consider it cheaper than a class feat
- you know something is horribly weak when you double its damage output and it is still worse than other, existing options (especially when it does nothing but damage)