Tested my lvl 30 character using Whetted Wedge and Lightning Enchantment Utility Rune. In level 30 zone proced chain lightning deals 165 damage, in zone level 22 it deals 81, in zone level 8 it deals 23. Tested with second character on different realm, same results.
It also does not scale with affixes “Damage increased by 15% after parry” on shield or “Damage increased by 15% after Damage Dodged” on pants. That might be intended behaviour, not sure.
It does not seem to scale with monster health as it was dealing same damage to elite/large enemies as well as small chaff.
I don’t think it should be scaling this way - maybe character level is more appropriate.