What Triggers Life/mana Steal?

What effects life/mana steal? And is it guaranteed or just a chance?

I know that melee effects both, and that it's chance-based.
I know that exploding effects life steal, idk about mana steal. But it's a guaranteed trigger.
I believe that thorns triggers both, chance-based. Just like war scream. (however I don't know about the mana steal on war scream.)
And I've heard that bomb arrows arrow triggers life steal. (same chance to as a melee hit, I'm assuming.) Idk if it triggers mana steal though. I'm assuming it does since it charges your powder special, so it probably has the same properties as a melee attack.

But are there any other things that trigger 'em?

 

Exploding. Melee. Warscream. Idk if thorns does anymore.

 

Can confirm arrow bomb triggers life steal, not guaranteed tho. Also charges powder special. idk about mana steal

 

Every hit where you do damage to any mob (except poison) has a chance of triggering lifesteal

 

Most spells don't tho

 

They do. It's just unlikely.

 

Really? :o

 

I've had lifesteal trigger with bomb arrow before, but I would guess that it's scaled depending on the spell. (Arrow storm probably has a low chance)

 

Arrow bomb is weird. If you hit with the arrow it triggers, but otherwise, it doesnt