Their personal quests:
Sera: We organize an operation with her 'friends', it goes south and people die, Sera gets angry and lashes out (unless you have the nobility knowledge perk). Good intent, poor planning, bad consequences and anger at it all. That's Sera in a nutshell. Having the nobility knowledge perk makes this quest more interesting because it shows Sera another way to do things. We know she appreciates it because we get more approval that way (after a slight drop). The goal was to help people and it's possible to get a good outcome. Either way it shows Sera understands how people work.
Blackwall: Find Grey Warden stuff. We know why he wants to learn more about them. The interesting part is that he believes they are super good guys out to help people. He knows they recruit thieves, murderers and other such unsavory people, but he thinks they offer a chance at redemption. It inspires him to do the right thing in that later quest of his. Giving him a chance to redeem who he is also gives us the card where he rides a griffon. He's big on people overcoming their failings and becoming a force for good. The goal is also to help people, starting with himself. A good outcome is possible. Blackwall also knows how people work.
Vivienne: Get a wyvern heart to save her lover, the aging duke. Not entirely selfish, but it is still in her interest. It doesn't work however you go about it. Reverse aging? Seeking to control nature as it were? It shows a poor understanding of the wider world, fitting with her narrow view. She only knows the Circle and the Court. She's a social and political expert, but when it comes to the realities of the world? She's delusional. She thinks she can control something so much bigger than her and she really can't. In the big picture, her efforts mean nothing.
Sera and Blackwall can make a difference in the Inquisition: Sera gets us the jar of bees (most awesome grenade ever!) and Blackwall lets us get conscripts for the Inquistion (war table mission). Vivienne? She contributes very little (we get some influence points through her war table missions, but still...).