It's more about how good a writer the author is than what past he/she gives his/her characters. A good writer can handle most kinds of characters and back-stories without them getting flat, stereotypical, exaggerated, unrealistic, too powerful...
and a good writer knows when it is appropriate to give a character a tragic past and when it is just awkward.
And a bad writer will screw up on everything and never manage to keep any character even halfway interesting.

That said, I am guilty myself of concentrating too much on one of my OCs tragic past in one of my fanfics (not on dA but on fanfictionnet). Her past is necessary for the story. It wouldn't work without it but I need to tone it down.