No. A story driven DLC should make sense to the protagonist involved in it and add benefits that can be used during the main story. Warden's Keep while not directly connected to the main story it allows The Warden to get a storage chest and one of the strongest swords in the game in Starfang as well as gaining the power of blood increasing there control of the taint in there blood, it also gave us more fereldan and warden lore. I think this DLC for DA:I makes since because it fits with the Inquisition, It is more then just about getting info on the last inquisitor and how the inquisition was back in his day, even though that information is important for a revived organization to learn there accurate history. But I think people are missing the point that even after cory is beat the Inquisiton has a job and one of the main jobs of the inquisition is to stop heretics and cults from bringing gods and demons in the world that can cause chaos. Just how the golems dlc while not connected to The Warden the fact it was in the deep roads and The Warden is a well known hero by that point it makes sense they was contacted. The same is said for the Inquisition because if the circle, templars and seekers obviously are in no position to stop the threat then who else? I would rather the Inquisition do a job that makes sense for them, stopping a cult fits them more then going in the deep roads to fight darkspawn which would fit the wardens. I would not expect the wardens to deal with this threat unless it gets to out of hand. This is also a incomplete mission by the old inquisition and while I wish it was more story driven and had more cutscenes the fact we already dealt with Avvar all this DLC did was expand on a group we met in the game already its not like they were randomly added in, this mission made more sense then fallow mire in my opinion with them randomly kidnapping our soldiers in a area I expect the Chasind to be. Not all DLCs have to be main plot driven because what hero has only one quest and journey? The Warden did more then kill the archdemon, Hawke did more then fight the Arishok, this is the legend of the Inquisitor and fighting a God is never a bad addition.
Edit: Plus defeating a Avvar God is a much needed feat for the Inquisitor, The Warden has defeated many powerful named foes, and Hawke has defeated more then the Inquisitor so far. 10 dragons while nice does not compare to a god and now we are getting some stronger foes under our belt.