User blog comment:IamJakuhoRaikoben/Chapter 355: Song of the Fairies, Review./@comment-6299840-20131011225313/@comment-7418318-20131015085149

Haku did NOT hit them in vital spots. While he told Sasuke and Naruto he was going to kill them it was later revealed that he INTENTIONALLY avoided vital spots.

And it's funny that you say that Lyon has nothing to do with Erza, while bringing up Haku from a completely different series...

As for the matter for skills and calmness... stabbing Humans in a way that won't kill them, even if the wound goes unattended is far harder than killing a person, especially if it's with big weapons like the ones Erza propelled. Gray was able to survive the stab wound because he stopped the bleeding with his ice magic. If the victim doesn't have magic that can do that or if the victim is unconscious, they'll just bleed to death.