Damage Over Time Question

I've tried searching for this, but always get 3 million results (even when searching for "damage over time")
Anyway - "10% Increased damage over time" - does this imply that I have to have some sort of thing that already does DoT? I have a Viper Strike gem which I guess would qualify, is there any other DoT stuff to get - there are quite a lot of nodes with this so I would imagine it's quite useful?
Or does the skill just take a fraction of your normal damage and apply it over time anyway without any other necessities?
Sorry for being so dense about what I guess should be reasonably obvious :-)

Since it only increases the DOT damage, you need to deal some of that in the first place. Examples would be: Contagion, Essence Drain, Bleed and Poison.

Brilliant cheers - what I thought, but not what I hoped :-)