It specifically states damage over time effects, as in DoT. So that would not remove any other "Debuff", otherwise it would have stated it along the lines of "Removes 1 detrimental effect".
EDIT: Sorry OP, forgot to answer your question.
What they mean by that, if a enemy hits you with an ability that makes your character take damage for like 10 seconds, using dark cloak will remove the 10 second damage from you.