A couple of clarifications and questions

[vaudeville]

Scratch that last part. It is working when I switch to Zeal but not Smite sometimes. Is it that there needs to be some arbitrary minimum amount of damage I need to do (obviously above 0) to activate such?

[Mephisto]

The minor effects are a few: Smite can apply Crushing Blow and Open Wounds, but not Deadly Strike or elemental damage like fire etc. It doesn't receive any extra damage from the Sanctuary Aura.

Three aspects are however very important to remembed when using Smite

-Smite is not affected by Attack Rating, so it never misses its target, regardless of defense and level of the target monster.
-Smite does not work with Life/Mana steal. This is a major drawback in alter difficulties, as many melee classes rely heavily on life steal to stay alive.
-Smite can however steal life through Life Tap / Life on Hit.