She has no reason at all to believe that Jon Snow has king's blood in him at all though? I just assumed she was doing the ritual as best she could guess based on her understanding of other magic that she is more familiar with.
At the very least, Stannis believed Jon to be a Stark, and they were kings in the north at one point. (And obviously quite recently, Robb was King and he was at least a brother.)
Melisandre seemed to know more, saying that he has a power in him and needed to embrace it. I don't know if she knows his actual parentage, but I think there's enough there to assume "royal blood" that she is fond of using for her spells.
I think Mereen is a necessary evil. When you look at the grand scheme of things, Dany had to have a maturation period. Martin knew he couldnt have her find redemption so swiftly, as the entire story revolved around her and her dragons. If she would have peaked in the middle of book 4 or something, the story wouldnt have had the longevity it needed to really have that all encompassing impact.
He could of had her conquer the entire Essos hemisphere, or perhaps had her rule pathetic subjects at Drogos side. Maybe even landfall in Westeros but struggle to consolidate power etc. But he chose a certain narrative to support his grand design later in the game. She had to learn how to deal with people and develop as a leader. Mereen was merely a vehicle for this to take shape. If Danys story was expediated forward it would have extinguished a ton of Westeros intrigue and story lines that unfolded instead of developing organically while she gathered support and resources in Essos.
It might seem like an excuse but Mereen is simlply there to lend weight and credence to Dany as a character, but sadly it takes away those very things to a lot of people because they feel like the Mereen narrative is a waste of time.
In the book, I think there's an actual quote from Dany saying she is going to "Stay, rule and be a queen." Like I think it's specifically mentioned that she needs to learn to rule a city before she can think about conquering kingdoms.
Who else has even tried to interact with them in the way Dany and Tyrion have?
Brown Ben was well liked by her dragons; he says he has targaryen blood in him when an ancestor married a dragon princess.
As for the episode itself:
I'll be honest, I'm super fond of the understated resurrection. It puts more emphasis on Jon being alive than the fact that he was resurrected. By that I mean most of us assumed he would find some way to come back; it was easier to figure it out in the book because we had so many examples of people cheating death, and in the show not so much. (Thoros rezzing is mentioned, but we don't get major glimpses of say, warging saving people and obviously not LSH.) But when you put him alongside others who had died in grandiose ways, Jon was maybe the only one whose story wasn't "done". It made so much sense that he came back, that him showing up in a burning pyre would have been so god damn cliche. The fact that they try to rez him and you go, Oh well here we go. THEN it doesn't work, then dude just comes up coughing for air? Yea, that was way better.
Ramsay/Roose - That went as expected. I figured the child being born would come into it, and as soon as Roose got close to Ramsay and reaffirmed Ramsay's position, I was like, bitch you are so dead. It just played so false. "Ramsay, I swear on me mum you're still my favorite. For real though."
As far as Davos asking Mel, it did play a bit false, but I think that it's passable because 1) They've used so many god damn shitty writing attempts to connect the dots already that this is the smallest sin and 2) Davos at this point has seen his son accept Mel's religion, and has, in the past, urged Stannis and others to ally with the Starks for the good of the realm. Stannis respected Jon, and both Stannis and Jon knew that the realm needed to be allied to defeat the true threat. I don't think it's too big of a leap to think that Davos could see Jon as being the only potential person to do what Stannis would have done, and possibly the only person with a claim to do so. He's seen some crazy ass shit go down with Mel; it might have been a desperate reach but I could see him making it. Maybe in a "throw the dice, what do you have to lose" kind of way, but yea.
All in all though, shitty writing aside, I liked this episode because THE GOOD GUYS WON. I mean, other than Ramsay. I like Roose in a sort of Darth Vader way, and I liked his actor, but I was fairly certain I knew how that was ending. But the wildlings putting down the Night's Watch, Jon coming back, the dragons being freed, Arya (assumedly) passing her test, Sansa having a real plan, and Euron coming into the picture; (Is Victarion a no go for the show? I can't remember.) just, fucking, raking in the points for some of the cool shit that we hoped would happen.
It's possible you could fuck over every storyline but as long as Jon fucks up some shit after his rez, I might be able to forgive it.
(That is a lie, stop fucking up my show.)