Remember when you killed Wrex in Mass Effect, and he didn't show up in Mass Effect 2, making Krogan relations a less pleasant experience for the rest of the trilogy? Well, those types of decisions don't have as much of an impact in Dragon Age. You can seriously poison Leliana with the ashes of Andraste in DA:O, and she’ll just come waltzing into a room in DA 2, saying she was miraculously saved by the Maker. It defeats the point of making that choice in the first place.
With Dragon Age 3, choices need to matter within the game as well as for the franchise at large. However, BioWare’s got a bit of a problem here when it comes to incorporating the events from the first two games. For one, the two titles were stand-alone stories separated by a decade within the world, and then also, Dragon Age 2 alienated many fans, to the point of having them give up on completing it entirely.
The solution would be to treat these two titles as canonical prequels, but start anew with Dragon Age 3. From here, BioWare could plan the franchise from the get-go as a trilogy--just as it did with Mass Effect--and bring cohesion and consequence to the storyline. Easy enough, right?