I think the idea with Stockpile is that paired with Braids you'll never run out of fuel.
This.
Hidden Stockpile as a sac outlet is a worse card than other options like
Evolutionary Leap. It is much better than most options when paired with other cards that require you to sacrifice stuff, like
Braids, Cabal Minion and
Smokestack. The main attraction of Stockpile is the revolt effect, not the sac ability.
Re: Curse of Stalked Prey is a bit too much for my liking. I once put it in with the idea that it was a "fixed"
Curse of Predation, but Curse of Stalked Prey can get out of hand just as fast, even if it's a little bit harder to get going. The problem is mainly that it snowballs out of control when your opponent effectively can't block for a turn.
Demonic Rising looks fun! No idea how good it is, but I assume it ranges anywhere from poor to good depending how many creatures your deck can put out vs how many it can keep on the table?