Amnesia is just overcosted but is is still a strong effect, I think it even got put in The Deck after Mind Twist was banned. My own pick, Erosion, is overcosted and useless but at least you cast it and then it doesn't hurt you. Sorrow's Path is really a triumph of poor card making. It hurts you taking away a land drop and then it hurts you when you use it. Not too mention it being convoluted and highly situational.
Sorrow's path looks worse than it actually is. It has a narrow effect, but Dark water's effect is even narrower. That card is obsolete in every aspect. I can imagine that one instance where Sorrow's path would be benificial: in reject rare draft, Sorrow's path is a bomb. Dark water isn't. You need double blue to cast it, the only perceivable use of the card is to get to triple blue. Now, I can't imagine a use for 3 blue mana, and even if I did, if you'd have an island in place of Dark depths you'd have 3 blue mana.