You are healing a PUG, and someone rushes: you don't have time to cast Elemental Drain before the fight starts. What do you do? Do you apply first your debuff then your buff, or the opposite?
See, about the time someone runs ahead and starts the fight without my healer, I'm thinking "You aggro it, you can stay alive until I get there. And I'm not rushing."
When I get there, I'll heal whoever needs it and then do the usual rotation of buffs/debuffs, HOTs and damage.