1. There are no experience orbs after kill mobs by Spark
2. Spark is 1st tier, but is overpowered by damage in comparison with other 1st tier combat spells (Harm or Ignite + Harm).
   But for 2nd tier Spark + Discharge is more or less OK against Ignite + Flare or Freeze + Cold Snap
3. Looks like Spark does not turn on aggro of neutral mobs, at least Spark + Kickback does not force to fight back Valkyries from Aether mod

I hope, the combination with Discharge will work after fix?

I just tested more spells and looks like they are unusable for combat. Not sure about open new Issue, because I may be have wrong understanding.

Charm:

I'm standing on high grounds and swarm of zombies are trying to achieve me. I use Charm + 8 Amplify to Zombie, it switches him "Enthralled" status, he stops for some time but does not try to attack his brothers. To spell start work, some of them need them to hit me at least once, and charm only one of them before, it's not very useful for fighting.

Envenom
Looks like Zombies, Skeletons, Spiders are immune to envenom, only Creepers are vulnerably, but Creepers are not the case when you can wait until the spell finish monster, and it requires many Amplify even with Poison Spore to achieve decent damage. Probably it will be too week for bosses, looks like almost not useful.

For 1 & 3 it's because it was not marked as entity damage but generic lightning (waiting main Ars to update to release the fix)

Regarding 2, it's a spell that deals 3 damage compared to 5 of harm. It only gets a powerup under rain and water to reach 5-6 damage, and the debuff is useless without the other two electric glyphs, while being slightly more expensive. Not to mention that if used in sequence with discharge you either add delay or lose those 3-6 damages due to iframes.

Oh yeah, another side effect of using the same damage type of lightning is that shocked buff triggers. But it won't after the fix, as it moves to its own damage type

My tests for Spark (archmage book, no focus)

zombie (dry):
spark kill with 4 hits: 20 -> 17.1 -> 11.2 -> 5.3 -> 0
harm kill with 5 hits: 20 -> 15.1 -> 10.2 -> 5.2 -> 0.3 -> 0
spark + amplify x 2 kill with 2 hits: 20 -> 13.1 -> 0
harm + amplify x 2 kill with 3 hits: 20 -> 11.1 -> 2.3 -> 0

Spark is better probably because of damage is increased with "shocked" state. But I think I was wrong and you right, balance is still OK. Spark should be a bit better because it's not default spell and need at least some game progress to get it. 2 hits to kill is OK, 2nd tier spells also make kill with 2 hits, but they have area effects, so balance is OK.