You're selling Hawke short, OP. I don't know how you played your game, but in mine, Aveline couldn't stop praising all the good deeds my Hawke had performed. While it's true that Hawke couldn't stop Anders, he did help to minimize the damages after the explosion. He stopped Meredith and Orsino, and managed to gain support from just about everyone in town who wasn't a zealot or a bloodmage.
Here's just a small list of enemies that Hawke fought against to protect his friends and the general public: slavers, raiders, thugs, darkspawn, assassins, demons, corrupt Templars, bloodmages, abominations, Qunari, Tal-Vashoth, and rock wraiths.
No, he couldn't save everyone and he couldn't stop everyone. Most of his family died, but the hardships Hawke suffered in life helped mold him into such a remarkable person. Despite all the tragedy and looming dangers, he managed to rise from rags to riches and become one of the most powerful and influential people in Kirkwall. Nobody is trying to claim that Hawke is godlike, least of all Cassandra. But the feats he's pulled off aren't anything less than heroic. A lesser man would've died before even going on Bartrand's expedition.
Hawke saved lives. There are people who are alive and well today because of Hawke, and I don't think it's fair to neglect this fact just because he wasn't able to save everyone. Feynriel now lives in Tevinter and helps save people through his dreams; Lia was rescued from a crazed murderer and joined the Guard; Orana was saved from slavery and was given a paying job by Hawke; Emile de Launcet was aided in leaving the Circle; Ella was rescued from Ser Alrik and has become good friends with Bethany; Alain was saved twice by Hawke, and received a pardon from execution; Keran was proven to be free of demon possession and was allowed to remain a Templar.
Those are all the people I could think of off the top of my head of whom were saved by Hawke.
If we're going to start labeling people as heroes only when they pull off extraordinary, godlike feats that prevent all deaths, tragedy, and warfare, then the pool of heroes just became so exclusive that even Spider-Man and Superman aren't on the list. Both of these heroes have suffered tragic losses in their lives, have witnessed catastrophic horrors that they couldn't prevent, and they even at one point became enemies of the public.
Bottom line: Hawke was dealt a bad hand. He lost his father and home to the Blight, lost his brother to an Ogre, lost his sister to the Circle, lost his mother to a serial killer necromancer. He was dirt poor when he arrived in Kirkwall and his opportunistic uncle sold him into indentured servitude for a year. Out of all that, Hawke was able to rise up to be the Champion of Kirkwall. No, he couldn't stop the inevitable, but he at least managed to dampen the blow and make sure Kirkwall wasn't wiped off the map.