I finally finished DAO and expansions on Nightmare, and I have some thoughts.
First and foremost,
@Ishtar is right, expansions set up reveals from DA2/DAI/DAV all the time, as fucked up as DAV execution is, the core is most likely taken from Gaider's lore bible. Not something I enjoy as I like ambiguity of DAO (though I can't stop thinking how it would be executed if DAO's direction was kept in next games). The biggest disappointment is the very end of Witch Hunt with Warden crossing the Eluvian with Morrigan. All this setup, and for what, exactly? Trashfire that was DA2? A single letter in DAI? Out of all mistakes BioWare made with the series, ditching the Warden as a protagonist must be the worst one.
Architect in Awakening is very compelling, interesting character. Too bad that he was completely and utterly forgotten. The consequences of sparing him are huge yet they remain untouched throughout the next games.
Companions in Awakening are great, it's a shame they have so little screen time. I like Sigrun the most, and I really hate how dirty they did Anders in DA2. In Awakening he's a man who just wants to be free and is shown to be sensible - if he's brought to conversation with Wynne, he declares the idea of splitting Circles from the Chantry to be madness. I'm unconvinced of his merging with Justice, he's very sceptical of the idea of fighting the opression of mages.
I played as an Arcane Warrior and I'm not impressed, I read a lot about this class yet it's boring mage that fights in melee as most spells are too expensive or take too long to cast. And I honestly expected more out of the Nightmare, with few exceptions the game is quite easy even on this difficulty. Harvester was probably the only really hard fight but it's too easy to cheese with bronto and taunt.
All things considered, DAO represents the very best of BioWare and should've been a standalone game, with maybe Awakening as an expansion. BioWare's vision and culture changed too fast and too much (as evidenced by next games, be they DA or ME sequels) for the series to have any chance.
Sidenote, Owlcat just announced their shot at the big league with The Expanse: Osiris Reborn. BioWare is supposedly working on next Mass Effect, it would be funny if their flagship series was snubbed for the second time, first time being DAV by BG3.