Well the reason I figured DA2 helped with Inquisition is because of the whole mages/templars thing.
Technically, sure, but you don't really need to play DA2 to get the idea of "mages and the Chantry are fighting now." Especially since DA2 doesn't really elaborate on the overarching conflict that much (ie, the entire civil war basically happens between games regardless).
And ironically, the canon version of events is that the events in Kirkwall aren't really what triggered the conflict anyway - the plot of DA:I mostly sort of ignores that aspect of DA2 in favor of expecting you to read one of the novels (specifically, Asunder). You can get some idea of what happened in it by talking to Cole, but he's cryptic and weird so it's hard to understand a lot of what he says unless you already know it from having read the book.
A lot of stuff in DA:I comes from the novels - there's a ton of stuff about Fiona from there, and something like 80% of the Orlesian storyline comes straight from the books. They basically made the same mistake I think 343 made with Halo 5 - ie, tying the expanded universe media into the core narrative of the games to encourage more people to buy them, and in the process watering down what made the games worthwhile in the first place and alienating a large chunk of the potential fanbase. Something like 95% of Halo 5's plot pretty much NEEDS to you have read about a dozen books beforehand to really understand.
The DA2 Legacy DLC revolves almost entirely around Corypheus, though, and has a bit of influence on the whole Hawke/Grey Warden storyline, which makes it far more relevant than almost anything else from DA2. Varric will sum up those events if you talk to him about it in DA:I, but still.
ME3 had that issue too. I was a little miffed that my Councilor Anderson decision made fuck all difference in the grand scheme of things. ---