Centaur Warrunner has a passive ability, "Return":
Centaur Warrunner immediately counters every attack, damaging the attacker based on a percentage of Centaur's strength.
Base Damage: 16/18/20/22
Bonus Damage as Percent of Centaur Warrunner's Strength: 26%/34%/42%/50%
Source: http://dota2.gamepedia.com/Centaur_Warrunner
If an enemy hero uses a DoT ability, does Return activate on each instance of damage and do "returned" damage to the caster?