While the 1st season decently balances tension and drama, the 2nd season ramps up all the bad of the 1st, and dampens the good.
Perhaps most notable is the transformation of Henry from a nihilistic, bitchy, teen rebel into a nihilistic, bitchy, teen rebel. From that point the character doesn't grow. It's okay in the first as the viewer can see that she struggles, in the second it gets old, and it's not delivered as carefully. There's some development in her behavior to 'the accident' in the 1st season, but it's entierly stagnant in the 2nd season, and the viewer is supposed to just go along with it.
Indeed it seems like no character grew much at all in season 2. While the story does progress, it's so slow that it could have happened in all of 3-4 episodes (instead of 10). That's basically the same for character arcs. There's some attempts at PTSD, but it's underwhelming at best, there's no build up, no tension, no payoff (or consequence).
Since I don't know better, I'd say this is an attempt to drag out the series ad infinitum rather than to make something good.
I'd give the first season a 9, the 2nd a 3 (this balances out to 8, I'm great in math!).