Each will include damage to one target, two targets, or all targets in an appreciable area (15-foot cone) as x1/x1.5/x2 if applicable. We'll also assume that persistent damage lasts for 2.5 rounds on average, according to comment from asker. Two entries will exist for each spell not targeting Reflex, the first assuming a Moderate save (+12) and the second assuming a Low save (+9).
- Electric arc: 3d4+4 = 11.5 (6.325/9.4875/9.4875)
- Scatter scree: 3d4+4 = 11.5 (6.325/9.4875/9.4875)
- Spout: 3d4+4 = 11.5 (6.325/6.325/6.325)
- Spout near body of water: 3d4+4 = 11.5 (6.325/9.4875/12.65)
Cantrips Targeting Saves
- Ancient dust: 1d6+4 = 7.5 + 2P* (7.5/11.25/15) (9.625/14.4375/19.25)
- Chill touch: 3d4+4 = 11.5 (8.05/8.05/8.05) (9.775/9.775/9.775)
- Daze: 1d6+4 = 7.5 (5.25/5.25/5.25) (6.375/6.375/6.375)
- Disrupt undead: 3d6+4 = 14.5 (10.15/10.15/10.15) (12.325/12.325/12.325)
- Gale blast: 1d6+4 = 7.5 (5.25/7.875/10.5) (6.375/9.5625/12.75)
- Haunting Hymn: 1d6+4 = 7.5 (5.25/7.875/10.5) (6.375/9.5625/12.75)
- Puff of poison: 1d8+4 = 8.5 + 3P (10.575/10.575/10.575) (13.1/13.1/13.1)
- Torturous trauma: 3d4+4 = 11.5 (8.05/8.05/8.05) (9.775/9.775/9.775)
Cantrips Targeting AC
As above, but we'll assume a spell attack bonus of +11 against a Moderate AC (21) or Low AC (19). We'll assume splash damage can hit multiple targets if present as above, though that's really just for acid splash's sake.
- Acid splash: 1d6+4 = 7.5 + 1S + 2P* (5.7/6.175/6.65) (7.7/8.175/8.65)
- Divine lance: 3d4+4 = 11.5 (6.9/6.9/6.9) (9.2/9.2/9.2)
- Gouging claw: 3d6+4 = 14.5 + 3d4P* (9.6375/9.6375/9.6375) (14.4125/14.4125/14.4125)
- Phase bolt: 3d4+4 = 11.5 (6.9/6.9/6.9) (9.2/9.2/9.2)
- Produce flame: 3d4+4 = 11.5 + 3d4P* (7.8375/7.8375/7.8375) (12.0125/12.0125/12.0125)
- Ray of frost: 3d4+4 = 11.5 (6.9/6.9/6.9) (9.2/9.2/9.2)
- Telekinetic projectile: 3d6+4 = 14.5 (8.7/8.7/8.7) (11.6/11.6/11.6)
Many spells targeting Moderate saves or Moderate AC do more damage than electric arc targeting a High Reflex save when facing a single creature. Only daze, gale blast, and haunting hymn require a single creature to have a Low save or Low AC to surpass.
Several spells still don't surpass electric arc in damage when faced with two opponents in 30 feet, even with a large disparity in DC from High to Low. These include daze and several single-target attack spells (acid splash, divine lance, phase bolt, and ray of frost).
Outside of those five, all remaining spells surpass electric arc in damage against two or more creatures when targeting a substantially lower DC from High to Moderate or Low.