Don't nerf Annie's AA range, give her passive a nerf.
Annie isn't strong because she can auto you from far, her attack speed is awful and learning how to weave autos to abuse the range is actually one of the more skill-based aspects of her kit. Her biggest problem is that she can never be all-in'ed by a vast majority of her lane opponents because she can insta-drop Tibbers on you and then 100-0 you back.
Her stun passive never runs out. Letting her only hold onto the stun indefinitely lets her zone out melee champions like fuck. If it was like 10 seconds or 15 before it fizzles I think she'd be balanced.