On the positive side the family dynamics are quite realistic (homicide aside) as far as lies and difficult communication are concerned. It's believable that some traumatic family events are left unspoken and after the years passed, nobody wants to dig them up. Also, people tend to have different memories of the same events and to elaborate those memories as it best suits them.
Therefore, Danny's version is that he was the "real" victim, even if he was responsible for his sister's death, and desperately tried to shift the burden to John and even to his dad. However, regardless of Sarah's accident, Danny never took responsibility for his own life, which makes him an immature, irresponsible whiner with a mighty mean streak. Not a sympathetic character. I agree the actor did a good job playing Danny, but not even once I felt even remotely sorry for his character.
On the negative side, the flashback technique was maddening. All those fragments from the past related to Danny's demise, mixed with the chronological narrative, plus John's voice over, did not help to create a smooth and compelling narrative. Stretching the plot further is not going to help, because the plot was already quite diluted enough (13 episodes when 8 would have been enough). Finally, the police reconstruction of what happened to Danny is so flawless that I wonder how they'll manage to mess it up in the next season.