Latter
Would nerfing it to something like this below help?
Unupped= 5 Other for 4: Deal 3 damage to the opponent
Upgraded= 6 Other for 6: Deal 4 damage to the opponent
Unupped is actually a tiny bit worse than repeatable Lightning and is smaller, which should balance it out a bit
Upgraded is the same as repeatable Shockwave. Unsure about that. But meh.
As far as summoning cost, I don't even know how to try and get it correct.