A quest in Silverpine Forest mentions that due to the Wrathgate affair they're now working with a less potent version. So I would assume they can ressurect those killed by the plague.

Well, one thing is for sure, it won't end well for Thassarian. He's not going to kill Sylvanas. It leaves him with either killing his friend, fleeing with his tail between his legs, or dead.

I'm sad to see Uther's native city falling under Horde control. And I wonder what's the plan with Stratholme. Argent Dawn/Crusade are neutral to either faction, but Dawnbringer mentions things such as the "Bastion of the Silver Hand" being retaken (the building that is the "live-side") which I'd imagine the Silver Hand still being very much Alliance only, despite the existance of Horde paladins.

This raises a few questions for me:

1. What's the state of uninstanced Strat? I know that on live, the uninstanced city is laid out in that zone-space between WPL, EPL, and Ghostlands, but in addition to missing most of the doodads and decorations, it has an untextured Necropolis (Naxxramas) posted over an unfinished area in the backlot behind the Slaughterhouse. It would make sense if that were removed, if that area is actually flyable, and whether or not the uninstanced city changes after you complete the quests inside the instance.

2. What happens if you re-enter the instance after you've completed those quests? Does the Argent phasing still stand or are you able to complete the instance again?

3. Is any further explanation given re: Aurius and how he became Rivendare?

It seems in the recently available Silverpine Forest quests that Lord Godfrey an NPC from the Worgen Starting quest -who commits suicide rather than serve a Worgen King - is risen as a Forsaken. He leads the attack on Pyrewood and Sacks it. Sylvanas shows up to gloat about her victory when Godfrey makes his move and shoots her in the back of the head. Now before people freak out, Sylvanas is rezzed by one of her Val'kyrs at the cost of it's life. Obviously there is more information to this event but this is the main plot of it. Also it is said that the worgen curse makes you immune to the Forsaken plague (not sure if this is the val'kyr rez or the concoction they use on the ground in Gilneas). An interesting twist to say the least.

The Sylvanas event is definately cheap.

An almost mister nobody comes around and oneshots her. Come on. She has gone toe to toe with Arthas two times (and admittedly lost). It would be akin to Lady Liadrin judging Magni Bronzebeard to death before we are told of her lore position. In this world where we take hits to the head all day long, and gets giants stomping all over our little plateclad people, it just doesn't fit.
It only weakens Sylvanas needlessly. At the risk of sounding horribly cliche, it would have been better if he took a huge chunk of her life in that hit, but didn't kill. It would still be weak, but something we have seen before and something that is clearly part of the world's way of life so to speak.
And what does he gain? Could be Blizzard want him to be a badass hero with his own agenda. But this just smells of Giga Drill Breaker (if you are unfamiliar with it, it is an absurd overkill ability in an anime cartoon)... At least it isn't Rhonin who did it.

Could it really only be an attempt at making him a tough guy, and fast (the Marris way to do it is a lot better)? Or culd there be more to this? Like, karma will get you for all the crap you do? Would be interesting if it had some rather meaningful background, that might not yet show up. The newly raised Forsaken plot might work with a little help. But it would require a few events where the player needs to mop up some renegades. It would also be a good time to finally lay down the line of Sylvanas and her policy for living, or rather unliving. "Ah, X, our recent additions to the ranks of our warriors are proceeding well, but as often happens, a few things go wrong. In this case some of the recruits have been less than enthusiastic and have run off. Don't they know it is their duty to serve the Forsaken and their rightful Queen? Go rid us of that problem."
In essence, you can pick cookie 1 or 2, just know that cookie 2 is mine.
If it is only him (and possible the nearest undead)... then it becomes complicated. Is it because he is particularly strong willed? But then what about Prince Galen? He seemed like a pretty determined guy. And if that is the case, why him? It isn't as if Sylvanas needs more enemies, there would have been plenty dead people to use for that.

It just feels as if he isn't big enough, nor established enough for such a big thing.

Is there any news of Nathanos now that WPL is open? It would be a terrible shame if his death is canon and he's gone forever.

I highly doubt it, I am not in the Beta or anything but I assume he will be the head undead hunter trainer and be positioned in the Undercity now, or more likely in the new outdoor gardens above the Undercity with his blighthounds.

It might be construed as a (un)subtle reminder that we're not dealing with gods/godlike characters here. That, as big a figure as they are, they can be stabbed in the back by any assassin - if he can get into the right position, at the right moment.

That seems to be a new theme in Cataclysm. Thrall seems to be abducted by a bunch of SI:7 op unknowns (I doubt they're using legendary well-known heroes as covert ops), for instance.

This event is lore, not gameplay. A bullet to the head is a bullet to the head, even for a hero, even if that hero's undead already. Small wonder she doesn't have any memory loses, but then again, (in Warcraft) ghosts and thus banshees have a memory without a physical brain, it's likely connected to the soul or similar.

I understand that it is lore, and pretty much all goes. But the heroes and leaders of the factions, they are on a different level. I agree that it could be changed, but this doesn't really change that as she is the only one to suffer this. And as such she is just diminished, rather than all the leaders are taken down a notch. It is really hard to reverse 5 years of established 'nature'. And it would royally suck if pretty much all the leaders had some level 5 incident.
This come right on the heels, more or less, from Saurfang jumping out of te shadows and taking down a Sourge commander almost on his own (the Warsong Hold questline). You can't have both superheroes and commoners in one package.
But no, a headshot isn't a headshot. Not in this world. Lorewise we should have seen various bosses suffer that fate now and then. It just isn't a very strong event since they can't export it, it will have to be localized, making it a very strange thing. "If he can, why can't one of our guys?"

It doesn't need explaining any more then why you can drop a flaming meteor of death on a character in Final Fantasy and they shrug it off, yet an insane clown with a butter knife one shots General Leo in FFVI.

If the story in a game calls for something, it will happen regardless as to what the "realistic" expectation is