I should mention that I'm not one to be overly susceptible to nostalgia goggles, so when I was followed by a nagging impression that DAO's main quests felt more natural than DAI's, I went back to check and tried to find out what was different that could acccount for such an impression.
The observation: In DAO, we effect different outcomes by doing different things. In DAI, we do all the same things and effect different outcomes only by making decisions in a dialogue at key points - usually the end of the quest. In DAI, the divergence is usually almost non-present in the game itself, except for very minor differences.
Example: consider DAO's quest "The Arl of Redcliffe". You have three main outcomes - Connor alive and free, Connor alive and possessed, or Connor dead. There are additional variations resulting in "Isolde is dead" or "Isolde is alive", depending on whether you called for the help of the Circle or not. The important thing here is this: while some of those outcomes are decided in dialogue, you actually do different things to make them happen: you kill connor, you go to the Circle for help, you let Isolde sacrifice herself, you either go into the Fade yourself or send one of your mages or Jowan into the Fade, playing as them.
Compare: DAI's Wicked Eyes and Wicked Hearts, the main quest with the most variable outcome. With no meta-knowledge, the first real decision you make in this quest comes immediately before the end, namely when you leave the Royal Wing. At that point, you'll have opened the halla door in the Servants' quarters to get Briala's stuff and the halla door to the lower level. You've also been in the trophy room to collect stuff on Gaspard. With no difference at all in what you actually did, you now have access to the three main outcomes - Celene, Gaspard alone and Gaspard/Briala through two decisions made in dialogue: let Celene die or not, and choose Briala or Gaspard if you let her die.
it's the same with other quests from DAO: Brecilian Forest - three main outcomes, you do different things: make peace, destroy the Dalish clan, destroy the werewolves. Captured: wait for your friends, break out through deception or break out through force (and hey, the optional seduction would never appear in DAI because it couldn't be made gender-neutral without looking silly). Orzammar: at least the first part has significant forks. Meanwhile, you make two decisions in Here Lies the Abyss but don't do anything different. You can do two different things in What Pride has Wrought but that doesn't affect the possible outcomes, which are, yet again, decided in a dialogue scene.
DAI's missions lack complexity. When you play for the first time, you won't notice that because the presentation is overwhelming and the emotional impact tends to make you not pay attention to complexity, but it becomes rather obvious in subsequent playthroughs.
In comparison, it becomes all too apparent that the mission designers created the main plot missions on the principle: How can we get significant divergence in the outcomes with an absolute minimum of differences in what players actually get to do? We have one point with a major fork that doesn't follow this principle: the mage/templar choice. However, the missions themselves are again, completely linear and lack complexity. Meanwhile, in DAO it feels more like the designers asked themselves what solutions would be possible considering the characters and the situation, and then implemented them through actual dialogue and gameplay. DAI's main plot missions feel artificially constrained, DAO's more naturally evolved.
Which means, I have to rescind the statement I made in my diary thread. In terms of quest design and complexity, DAO still reigns superior. I did not post about this earlier because I thought I suffered from nostalgia goggles. However, a look at both games from some emotional distance makes the differences obvious.