I like that they showed Severus' ability and his anguish over Lily.
Severus is actually exceptionally powerful, able to conceal himself from Voldamort; it was not until there was direct evidence that Severus was a rival by way of the claim to the Elder Wand that Voldamort killed him, and without magical means, I might add. Furthermore, Dumbledore went to Severus for potions to hold off the effects of incurable dark magic.