The dark isn't so in your face as DA2, which everyone seemed to agree at the time was overdone; there were just too many sadistic Templars, too many blood mages and for the last two boss fights you had to suspend disbelief.
In DAI you are also perhaps expected to use your imagination a bit more. You see the red lyrium growing out of Fiona if you do Hushed Whispers but perhaps she should have looked and sounded a lot worse as a result; may be we should have been given a least one close up cut scene of a Templar transforming as the red stuff bursts out of them. We are told about the affects on people rather more than actually seeing it happen. Likewise, the Warden blood ritual. It looks pretty tame and we only see a couple of Warden's actually sacrificed but it is pretty evident from what people say that dozens, possibly even more have been used; elsewise how could they summon a sufficiently large number of powerful demons? I was happy enough with this; I don't have to be shown lots of gore to know what is going on.
As for the impact of war, well may be it was more muted in the Hinterlands but around the Exalted Plains it was very evident they had been in the midst of it. Florianne was a bit of a cardboard cut out villain but the fact that you could have all the pieces in place to save Celene and yet just stand there and let her get the knife was pretty dark to me. Then there are the judgements. Do you really need to see someone's severed head?
As for the companions, they seem to have a fair bit of depth to me, some more than others. Dorian's personal quest had a big emotional punch to it to me whether you are planning or romancing him or not. You get to drink with Bull's Chargers and get to know Krem quite well, so making the decision over them isn't about some faceless mercenary band. Getting to see the softer side of Cassandra is rather fun, particularly if you do involve Varric in the joke. That's not dark, I agree, but you only appreciate the dark if you get some lighter moments along the way to counter balance them and vice versa.
The only thing I would agree with is that the size of the game means that the stronger parts are wider spaced so could be said to dilute the overall impression of darkness which is why people seem to think it isn't there.