Hercules: Divine Hero doesn't yet have a listed market value on TCGPlayer at the time of writing, but the lowest-priced copy for sale on the site comes in at $200
(2014-05-29) If the spell being copied has an X whose value was determined as it was cast (like Skeletal Scrying has), the copy will have the same value of X
You need to build around it for sure, but the payoff is huge and well worth the effort
The mass creature stealing elements of Emrakul can decidedly turn the battle in your favor, especially since it's a permanent theft of those creatures since you sacrifice them all if Emrakul leaves the battlefield for any reason
Nahiri is a famous Stoneforger, and the powerful Stoneforge Mystic represents the average Kor lithomancer
Theres plenty of value here, especially with that cheap spell-copy ability, but Id rather put that ability to use in the 99 of a commander like Niv-Mizzet, Parun or Narset, Enlightened Exile