I dont even think they know whats canon most of the time.
Alister is probably going to be in DA:I.
I bet you anything he will be good old fun loving Alister, rather then whatever this comic Alister is.
Because people clearly like that Alister more. Even if he has been hardened.
And I support hardening Alister. I think it teaches him that the world is full of terrible people, and he cant just bend to their will. He needs to stand up for himself.
Maybe this will help you guys with the canon thing: (Quotes are all from David Gaider)
"The two prequel novels are canon-- there is nothing for them to conflict with.
And it is fine to assume that, if your particularly playthrough matches up with the events depicted in Asunder or the comics, those events occurred in the way they're portrayed and will be treated as such in future games. If your particular playthrough does not, then those events either happened differently or not at all. In a game we have the luxury of that kind of variability. In either case, you'll only see how it works once DA3 comes out".
And a few others for clarification:
"Alistair being King of Ferelden is not "canon", as in it does not affect the choices you made in your game nor override them. The comic is a tale based on one possible version of the game world... as it would need to be, being a comic book and not a video game, and thus unable to react to game decisions."
"All possible outcomes in the game are equally "valid", and there's no single canon that outside media are drawing from-- yet, anyhow, though that could work quite well if we wanted to do it that way.
So long as the stories told in comics or novels don't override your choices in future games, I'm uncertain of the source of anxiety regarding them. The choices have continuity between games because that's the only place where they can have it. If someone's looking for their choices to be reflected in comics and novels, they're being a tad optimistic... while I imagine it might be nice to have your particular game story be the basis for such tales, it's simply not possible to cover all possibilities without simply avoiding all references to earlier characters/storylines altogether. "
Hope this helps. 