tldr: Use gold for the beginning of the year and dust for the end of the year
I've been thinking about how to utilize resources (gold and dust) in the most efficient way throughout each expansion every year (for standard). Obviously, the first expansion each year will remain in the standard cycle for the next two years, so this incentivizes the players to build a large collection from this expansion to maximize the time they can play with these cards. As such, they spend more gold on packs and are more eager to spend dust on this first expansion every year. Similarly, the 2nd expansion will remain in standard for slightly less time and so players are slightly less incentivized to spend resources on this expansion than the first, and the same with the third expansion.
Now, the next key thing to realize is that Blizzard must constantly create cards that are more powerful than the previous expansion so that the meta isn't stale. Otherwise, no one would be buying new expansion packs and Blizzard wouldn't be making any money. As a result, the cards from the first expansion every year tend to be fairly weak, but the cards from the third expansion tend to be very powerful. We see this time and time again with Descent of Dragons, Kobolds & Catacombs being extremely powerful and other expansion like Ashes of Outland and Rise of Shadows being slightly weaker.
Using these ideas, it is clear that different expansions should induce different ways to collect cards from that set. Since gold is the best way to buy cards in bulk, gold should be utilized more toward the beginning of the year where more cards will remain for a longer period in the standard cycle. However, dust should be utilized at the end of the year where the more powerful cards warrant an immediate craft as they are meta-defining.
Now this is not to say that players should ONLY use gold for the first expansion or ONLY use dust for the third expansion. Ofcourse, there will be very strong legendaries that players have to craft in the first expansion and gold should be used to collect the rares/commons for the third expansion. However, when looking at the pros and cons of the resources in hearthstone, in my opinion it is a good strategy to incentivize using one over the other depending on when the expansion is released during the year.
I'll skip the epistemic part of your posting, because it would likely take me too long to go through it. There are two things about your idea or strategy or whatever you want to call it:
First, gold and dust should primarily be spend depending on which and how many cards you own from one expansion, especially with the new pack rules established with AoO. Unless you only want individual rares of a set and don't care at all for the rest, you are guaranteed to get all commons and rares from a set within 60-70 packs. It doesn't make sense to craft anything before you reached that point. And from that point on, you have to evaluate how many good epics and legendaries you are missing, and whether it's worth buying more packs (because you miss a lot and almost any new one would be good) or whether it's better to craft the missing cards individually (because only a few are worth it).
Second, while the last set of a year tends to be more impactful than the first, it's too simple to say that these would be the cards worth having. If you want your investments to pay of long term, you need to evaluate cards more carefully. First, you need to consider whether a card is good based on the cards in the current year or the previous and soon rotating year. If the deck you want to play largely depends (like 7+ cards) on cards from the rotating year, there's a good chance that the deck won't be good anymore after rotation, like Zul'jin and Spell Hunter after Rastakhan's Rumble. Next, you need to consider how likely it is for your deck to receive support from future expansions. For example, Reborn is a keyword that (likely) won't show up in future expansions again, so Making Mummies was always a risky craft. Finally, you have to ask yourself if the deck you want to play is likely to get nerfed. As DoD and AoO have shown, the developers have few qualms about nerfing cards anymore, as soon as 48 hours into an expansion, and as frequent as almost once a month. This is something you can't really predict, but at the very least, you should hesitate with investing large amounts of dust in the currently most popular decks.
It's largely up to speculation, whether an epic or legendary is worth crafting. Saving resources for the last expansion of a year can make sense, and with the current pack rules, Gold might be even more valuable than dust. But with all these things to consider, it's better to decide on a case by case basis.