How does the Smite effect work on Sky Splitter?

Solution 1:

First off, I am not sure if it stacks with a Barbian that is currently using Frenzy and a Smite rune.

Now to what it does:

The Smite effect works like the ability/rune.

Frenzy - Smite Rune: 20% chance to call down a bolt of lightning from above, stunning your target for 1.5 seconds.

I remember back in patch 1.04 or 1.05, my Sky Splinter was stunning, and doing damage when the smite occured (roughly 2k extra damage) on the enemies.

Source

Solution 2:

As far as I'm aware, Smite does not actually deal any damage.

Smite is simply a stun, so it's % chance to stun an enemy.