I actually quite like this one.
Merlin´s actions cause problems, but I get what he did. He never intended to kill Morgana, even in season 2 he just poisoned her because there was no other choice.
The dragon also didn´t say it was her destiny to die right now, Just that it would be for the best. And it´s in-character for him to not kill Morgana. He even saved Uther´s life multiple times, knowing exactly that his life would be a lot easier without him around.
He is just the type of character that doesn´t want to sacrifice anyone, if he can help it.
Everything that Merlin did was supposed to happen, since the vision in the cave showed all that.
When he pushed Morgana down the stairs she didn´t intend to kill Uther yet, she just wanted to go meet Morgause. But Merlin´s actions caused her to learn that she is his daughter, which pushed her to rush things and try to stab Uther immediately. So... yes Merlin made the situation worse, but he had good intentions. And I understand why he saved her. It was not to please Uther, but rather to spare Arthur and Gwen the heartbreak, since both of them were clearly distraught by Morgana almost dying. And Merlin just assumed putting her in a coma should have still changed events and prevented her assassination attempt for atleast a while, not knowing that the coma and the daughter reveal is what caused her to go with the dagger to Uther.
Instead of being annoyed with Merlin I´m more irritated with Uther and Morgana.
First of all, Uther´s hypocrisy. Magic is only ok when Uther needs it. When he needed to create an heir (Arthur) he uses magic, when Morgana is in danger, he uses magic. I guess we can atleast acknowledge that he loves his children, even if he sucks as a king, and also as a parent.
And yes kings have illegitimate children, but they don´t acknowledge them, unless they REALLY have to. Like if Arthur would die and he really needed another heir.
And seeing Gwen and Arthur be really upset about Morgana really annoyed me more with Morgana. Those people care so much about her and she just doesn´t care about that anymore and would throw them under the bus when she gets a chance.