I have yet to play Trespasser because I was doing other things besides video games with my free time and I decided I wanted to recapture those emotions you get when getting lost in a fantasy world.
From what I've picked up, Trespasser was a redeeming quality to this game for some. Without going into detail about story elements, can someone tell me why people gave DA:I a second look after this came out? (I also have yet to play JoH and The Decent so info on what makes them good is also welcomed.)
Overall, the Trespasser DLC is great if you want to expand on lore, the characterization of a now highly controversial character and resolution to the companion storylines. In addition, it also allows you to determine the ending of that organization which you helped create (the Inquisition).
But many consider the Trespasser DLC as the "real ending" of DAI (hence why some despise paying for it) and that's an opinion I couldn't disagree with more.
DA:I was about the Inquisitor and stopping the breach and Corypheus. The base game gave you that. It wasn't about the companions, or the nations or the love interests it was just about the main plot. Now don't get me wrong, companions, LI and so on are all important and deserve development but they are supposed to add to the game but it was never supposed to define the game itself.
The 'real ending' of DA:I was when you defeated Cory, but despite that, the story of DA as a franchise is ongoing. In addition to providing resolution to the more personal but often overlooked aspects of the main game, Trespasser is a gateway to help furnish the lore and story of future games.
And is in that that many people gave DAI a second glance after they saw Trespasser--it helped put the whole entirety of the main game (and prior games) in a new light. Where it provides resolution it also provides a sense of wonder and awe. So much so that you find yourself looking back on your main playthrough and wondering what you missed and what you think of it now that you know more.