You got me wrong there, I don't "hate" it, I don't like that it's part of this game as most of the SP was built with the same gameplay and both SP and MP influenced one another. What I said a few times is that I hate that SP characters are being put in the MP because they were SP characters to begin with. I also mentioned that I'd rather have a MP style Dragon Age as a separate game so the Dragon Age team could focus on a whole different battle system that wouldn't feel like it's ripped off from the MP. I like that the tactical menu is there in SP, it saves me a lot of trouble sometimes, but I do miss the old combat system from DAO sometimes or DA2. DAI isn't that bad, it just feels like it was built around MMO in mind, which is a bit alienating.
In other words, I just wish MP stopped influencing SP in BioWare games.
The only thing that the single player and the MP influenced each other on was the combat, and honestly, I prefer the combat in DA:I over DA:O and DA2 (and I'm one of the people who preferred the combat in ME1 over ME2 and ME3).
Plus, DA:I was made as a single player game first with the MP added on as a bonus. I'd understand if you had to pay for the DLC, but it's free, so I don't see how it's an issue.
Also, about the whole 'ruining headcanon' thing: just because BW does something in ME or DA that breaks your headcanon does not mean it's reasonable for you to get upset about it. BW's writing their own stories in their worlds; you're just going along for the ride. Getting upset because what you imagined happened to certain characters didn't actually happen is just ridiculous. Yes, I headcanon too, but within reason and I make sure my headcanons are flexible so that if something happens in a book or game that doesn't go along with it, I can alter it to fit better. Seriously, the fact that so many people get upset when their imagined situations for the characters in DA are proven wrong is incredibly sad. They're BW's universes; not yours.
EDIT: To be clear, I'm not trying to be a douche, it's just that stuff like this is annoying to me.