Thinking about this more, I think I may have attempted to simplify Card Value (CV)a bit too much, and that is really the crux of the issue. I think I need to define a few more terms
Hand: H, what is currently in my hand. This will drastically affect the value of other cards remaining in the deck. For example if I already have some key cards, it may be less important to draw more.
Intrinsic Card Value: IV, the value that the card has on its own without any synergy. This would typically be high for most cards in a "rush" style deck, or a "beater" deck where you just rely on pumping out big monsters. It might be lower for a deck where you are relying a lot on synergy.
Key Card Importance: KCI, whether this card is extremely important for this deck. In some decks, there may be a really special card where the whole deck is built around it. In which case this would be high, and a key card would be considered especially valuable. I think this is also a function of what is currently in my hand, so KCI(H).
This ends up leaving us with something that looks like:
Card Value = CV(H, KCI(H), IV)
Intuition tells me that for decks with lower synergy, KCI will typically be lower, and IV will typically be higher, and the reverse for decks with high synergy and focus.
If we were to chart Card Value, from highest to lowest (for a given hand), I suspect we would something in between two extreme curves. A deck with extremely high focus on just a few key cards would have very high value cards clustered towards the beginning, and lower value cards clustered toward the end. A deck with lower focus with higher average Intrinsic Value would have a much flatter curve.
Of course I think this model is still a simplification, since there is probably another variable that would affect some of these knobs, Inaccessible Cards, which could make a lot of cards in your deck lose value if there are too many important cards in there (i.e. graveyard, discard, banished cards. So if all my key cards are in the discard pile, the rest of my cards will lose a lot of value. I think this is an OK simplification to make since the importance of this parameter will only be much later in the game.