1) You have very clear notes.
2) FYI: Card Ideas cannot be accepted into the Crucible Polls until they have evidence (usually a link) showing the current art is usable.
Balance:
Precognition requires 1 card (itself)
Dark Offering requires 2 cards (itself and a creature)
Precognition draws 1 card (net 0 cards)
Dark Offering draws 2 cards (net 0 cards)
Dark Offering digs through the deck faster than Precognition and thus should cost more*
Precognition costs 2
|1
in addition to the 1 card requirement
*Dark Offering also costs the price of the sacrificed creature. However this can be as low as 0 quanta + the creature card.
So the minimum possible cost is 2
|1
+ the Dark Offering card + the creature card + the quanta cost of the creature (usually 0).
However minimum in this case is used as a rough low estimate for the correct cost of the card.