Seems like this would only affect those who were 1) ITM, 2) planning to get out before the close, and 3) didn't manage to do so before the halt. Also, those who were holding spreads where the price punched all the way through would have the wing auto-exercised - so the only ones who can get really hurt are people holding trades in which the price landed between the short and the long. Seems like that would be a rather small subset, no?
I agree that it's a risk people should know about. But then, trading pharmas and biotech is prone to that kind of crazy crap, and if anyone trading them doesn't know it, this will hopefully be a belated wake-up call...