I think the way Regina was written in Season 2 was the first major problem with the show.
Really disagree with you here. I think Regina’s story from evil queen to redemption might be the only arc they have done well. Is she better evil? Maybe. But her struggle on screen, (and Lana Parrila’s acting) I’ve actually really enjoyed, and would not loop into the jumping the shark conversation at all.
Hook had til that moment been awful, trying to kill Emma and Snow, working with Cora, trying to keep Snow and Emma from getting back to Storybrooke, shooting Belle to hurt Rumpel, being locked up in jail and then wandering off to help Cora again, taking part in the torture of Regina, stealing the bean.
And I also disagree with this. I think Hook was compelling up until he became Emma’s love interest. Colin O’Donoghue was so good at playing an evil pirate, and the he got so soft in season 4. It was tough to watch. what compelled me the most about Hook was trying to figure out where he stood and sided with. He was a mystery but also had very obvious intentions. And he knew he had to walk a tight line with working with Cora and getting his own revenge on Rumple when he himself possessed zero magic and could get screwed in a second. And yet, he talked his way out with words. And then, he fell in love with Emma and his character became bland and awful. The struggle didn’t feel real like it was with Regina.
He just became boring and decided he was done being all revengy and what not. If you’re going to say the show jumped the shark before season 4A, the point where they made CS shippers happy by putting Emma and Hook together was it.