Would have to rewatch that episode to see the tone of her surprise, I always assumed Thoros was kind of the laughing stock drunkard of the religion, so the fact he was showing a power that I would assume be pretty damn strong would be surprising as fuck, but I can't remember exactly how she reacted to it.
its not clear. I know, that scene made me go google more on her back when it first aired. because prior to that, I thought she might be a fraud. After that, I was pretty sure she was. Fakes immunity to poison, with other poisons. Wrong about Stannis. Fire sword explanation seemed fake. I questioned if the shadow babies were really Red god, or a false god. I mean sure, light "creates" shadows out of darkness.. but still..
Reading up, book Melisandra does seem to be genuine.
So the resurrection surprise has a few possible answers. He was more powerful then her, and that shocked her. She declared it impossible iirc. before he even said he had done it 7? times.. or, Magic is returning to the world, and she didn't think there as that much power for that reason. or, She is again, a minor witch, pretending to be a priestess.
Yeah, this episode bounced around too much. For a show trying to buy time... This could have been 2 episodes.
Dorne going nowhere, as noted. Its dumb, ties into a larger complaint, where this show treats main characters as gods. how the hell will those idiots rule a nation? Show will most likely not really touch on this. the only nation to revolt on its rulers is the slaver city Danny took over..
Dothrakyi horsemen. yeah, that didn't seem in character at all.