Can I use Darkness to have a chance to dodge damage from a damage over time tick or other similar effects?

I play a Demon Hunter, and I frequently raid with my friends. Demon Hunters have a defensive spell called Darkness that gives you, and all allies that stand within the area you place Darkness upon, a chance of 20% to avoid all damage from an attack.

The Darkness spell description is:

Summons darkness around you in an 8 yd radius, granting friendly targets a 20% chance to avoid all damage from an attack. Lasts 8 sec.

"Avoid all damage from an attack" is pretty vague here. What counts as an "attack"? If one could infer this to mean an "instance of damage," I'm wondering if I can use it to block damage from a DoT effect. I'm also wondering if it'll trigger on area of effect spells as well. Testing this spell is relatively difficult due to its 5 minute cooldown as well as its low chance of actually triggering the avoid mechanic, otherwise I would have discovered the answer to this myself.

Is something like dodging DoTs possible? If not, what are the actual limitations of the Demon Hunter's Darkness spell?