After reading the Arthas novel, here is my theory of why this plague was developed, and why it will turn out for the best that it exists.

There are several quests in Northrend, specifically the "Mattias Lehner" quest line and the conversations that Tirion has with Darion Morgraine, that try to drive home the power the Lich King has. His strength isn't the fact that he can blast you with one super powerful attack, nor is it that he is particularly gifted in melee combat. He gains strength as you lose it. It raises your fallen soldiers to use against you. This is how he overwhelmed Quel'thalas, and how the Lich King won the War of the Spider.

When you look at it that way, no humanoid race can ever defeat him. The Nerubians were not a trivial civilization, nor were the ice trolls. What chance do our races have?

But, if you can deny the Lich King the power to raise those reinforcements, and also to kill off his own troops in the process, then you have a chance. If the scourge overwhelm a position now, like the in the Wrathgate trailer, you have defeated one army. The original undead. However, you just gave rise to a new army. Dropping the plague and retreating might be a good option for whittling down Arthas' numbers.

What they are setting us up for, based on the mechanics of the Yogg Saron fight, is a situation where people die in your raid and are raised as unwilling soldiers for Arthas. A good counter to that, would be dropping some plague near anyone who died, and kiting the undead around until the plague kills them for good.

Granted that I'm purely speculating, but I imagine that Blizzard designers really enjoyed the Akama/Maiev part of the illidan fight. I'm sure that there is going to be something similar. It'll for certain involve Jaina, which gives alliance players some buy-in to the story. Sylvanas gives horde players some buy-in, except that she isn't super great to have in a fight... except now that she has the plague.

I'd say we'll see those two women fighting to stop Arthas, one out of love and one out of hate. That has a nice narrative ring to it.

I don't think entities like the Lich King, Old Gods, Demons really conform to needing hearts or other vital organs to live. ;P

As for a link between Arthas/Lich King and Yogg Saron, I don't think there is one. Yogg Saron is called the god of death simply because he's an Old God, and they bring about mass amounts of danger/death. Yogg Saron and the Lich King share none of the same powers, Yogg Saron shows 0 manipulation of the dead, he's completely and 100% about mind games, and control of his opponents.

Why isn't Sylvanas "super great" to have in a fight? She was formerly the Ranger General of Quel'Thalas, and is at least strong enough to beat a high ranking dreadlord into submission (at least for a few years). Faction leaders in WoW tend to also be the strongest fighters of their faction.

I would think the battle into Icecrown Citadel will have more NPC involvement than we have ever seen till now, not just limited to Faction leaders but also Kirin Tor and the Dragonflights. I can actually see from the Horde side having Thrall, Sylvanas, Hellscream and Saurfang there (maybe not for the final battle but the push into IC).

I, for one, will be very disappointed if there's next to no link between Yogg and Arthas. Why make the big deal of the scourge mining/using Saronite? Why have a captive forgotten one in the mine? How could 2 such powerful entities coexist on the same continent, both with influence throughout most of the continent, and not have some kind of interaction?

Sadly I'm pretty sure that we've seen all we're going to see from Yogg related lore.

Well the Saronite is a incredibly powerful metal so that's why a big deal was made about it. The captive faceless one was due to him coming out of the hole in the mine to see what was going on and getting captured. They weren't allies and were at odds with eachother but I doubt there will end up being anything that big.

The thing is, Yogg-Saron is pretty much around since the dawn of Azeroth. He's probably seen a lot of kings, warlords and necromancers across the millenia. To him, the Lich King is a temporary nuisance, if even that. Given that the Old Gods were smart enough to outwit even the Titans, I wouldn't be surprised if Yogg's already made plans involving the Lich King, or if he's already benefiting from the Northrend conflict.

She did that with the help of a lot of troops, if we go by the WC3 campaign.

Except in game terms, Arthas is stronger than Yogg. We beat Yogg without help (on hard-mode) whereas we're speculating that Arthas is going to need Tirion or faction leader help to down. I guess I'm ok with Arthas being more powerful than an old god because the old god is still partially imprisoned but if Arthas is powerful enough to kill him (which we presume to be the case because hes a couple tiers more powerful) then it they can't simply ignore each other. Temporary nuisance is one thing but Yogg would know he's about to pull down all the free people down on his little island.

I wouldn't look too into how it is shown in game though since a lot of it is for gameplay reasons and less about how powerful the being is. Even in the end I think the lore for Yogg-Saron will have him being defeated by the Keepers and some heroes (ignoring the hard modes) rather than just the players. The Lich King will be defeated in the same way with it being Jaina, Sylvanas, Muradin, the Ebon Blade, and whoever else ends up being there getting the main credit for his death. I think we are getting to the point where the explanation for us being powerful beings will be that we got aid from others more powerful than us.

Another thing that I read earlier is that the tortured champion in the vision is named Immolated Champion. Guess I was wrong with wanting to say that couldn't be Bolvar and it seems pretty likely that is the case now. We probably will see him end up being a boss in the 5 man Icecrown Citadel instance.

So, WOWInsider interviewed Tom Chilton about 3.1 and beyond, WoW Insider interviews Tom Chilton on Patch 3.1 and beyond

I find it very strange that Blizzard has still kept the 3.2 raid a secret and am thinking at this point that 3.2 will have no new raid, maybe just a new dungeon (that was discovered in the 3.1 files). At this point all we are hearing about 3.2 is how the Argent Tournament will expand greatly with it, and that seems to be the main focus for Blizzard (and the new battleground).