lightning is absolutely viable. i think it’s better than cold.
shock reduces enemy lightning resistance, and there’s no limit to how many stacks you can put on an enemy other than how many you can apply before they start to fall off. that makes it easier to scale lightning damage than cold, although both are viable.
check out this build for an example of how you can build one, although other versions are also viable: Surge Lightning Blast and Static Charger 0.8.1b