When you are wearing armor with life steal aura, any damage that is dealt by enchantments either on weapons, or armor, does not trigger to heal you. 

Steps to Reproduce:

[Step 1]Put on armor with lifesteal aura
[Step 2]Put an enchantment that deals damage on your weapon or armor
[Step 3]Lose some life, then attack a monster with just that enchantment doing damage (stand far away with shockwave, or just let them hit you with thorns). And see that you don't heal.

Observed Results:

You don't heal when the enchantment deals damage

Expected Results:

Expected to heal from any damage that you deal, be it with melee, ranged, or artifact damage, along with enchantment damage (however that is classified)