But what you're saying is difficult to quantify. Just how much do big decisions need to change the scope of the story? And what's a payoff, anyway? Isn't it the case that one person might think something has a great payoff and another doesn't? What's the "shape" of a story? If the geth survive and the quarians don't, isn't that changing the shape of a story even if it doesn't change the direction? Why not? Because it doesn't specifically affect the final mission? What kind of definition is useful that posits saving one race over another as a meaningless choice just because it doesn't give you a different option later in the game? There's not really a great reason why the quarian/geth decision SHOULD have a massive (ugh, i almost said effect) consequence for something like Priority Earth.
I can't quantify this because the answer will be different with different stories and different decisions. And even among "big choices" some will be bigger than others. So yeah, it is difficult to quantify. The fate of the geth is actually done fairly well, as it requires choices from two of the three games to resolve (even if I don't like the geth's sudden onset of Pinocchio Syndrome) But the Council? What difference did that make? Different faces at the Citadel? Saving or destroying the Collector base? Jack living or dying had a bigger impact on the game than either of these!
It's actually a problem that plagued ME2 and ME3 both. The status of given individuals only resulting in receiving an email or happening across them somewhere.
You say that the Divine decision isn't huge because presumably it won't feature in later games (the Circles are not restored with Leliana, by the way. I think you'd have a difficult time arguing that all three Divines are functionally identical). But the decisions you make in Southern Thedas will stand. Similarly, I can import two entirely different world states from Origins. Do they have a HUGE affect on Inquisition? No. Do they need to for the decisions you made to still matter? Not really. Now, you could make an argument for something like killing Leliana. I think that's a good example of your choice not mattering. Inquisition fixes this, however, with the reveal about a slain-and-resurrected Leliana towards the end. That Leliana can be killed, revived as a lyrium ghost who then disappears in one playthrough, and be the lover of the Warden who eventually becomes Divine and abolishes the Circles of Magi in another, should dispel the notion that choices can't matter in continuous world states to the degree that they are mutually exclusive.
If Leliana is Divine, VIvienne creates a new Circle herself. And it comes to rival the College.
And Dragon Age is making the best of the save imports by having a different protagonist with each game and moving the setting from region to region, thus minimizing the baggage each game carries. But they can only keep that up for so long.