Will casting an aura on a creature with heroic trigger the heroic ability?
Heroic only triggers when "you" (the controller of the creature with heroic) cast a spell. So no, your opponent's Battlewise Hoplite will not trigger if you cast Crippling Blight on it.

Aura spells do always target when cast, so it will trigger heroic if you cast an aura spell and target a creature that you control with heroic.


  303.4a An Aura spell requires a target, which is defined by its enchant ability.