I feel like that kind of perspective is completely out of place here; it has its application in a TCG, especially one with formats based around constructing decks from drafted or random cards, but not a cRPG, especially not one where the majority of content is based around creatively and tactically applying the same toolkit repeatedly.
Almost all of the 'useless' spells have a clear intended purpose, it's largely their execution or place in the flawed or supportive systems that makes them a mockery. Even skills that aren't 'useless' are largely overshadowed or undesirable because of bad implementation or poor supporting systems.
That said, my vote is for Smoke Cover because it isn't just bad, it's almost always actively harmful.
