Ummm, Amatrine, you obviously didn't pay much attention to the Arthas novel. Sylvanas knew completely that the new plague could kill the living just as it could kill undead. She knew this, and encouraged it because she has some sort of misguided vendetta against the living. She simply manipulated Thrall in order to cover her own ass and get Varien to target him instead of her. On top of that, to the author of this article; you say it is not a defense of the horde, but really it is, and not a very good one at that. To be plain and simple: Thrall is incompetent. His greatest weakness is putting too much trust to those who don't deserve it. Right from the start, he should have noticed that Sylvanas and the Forsaken needed a little observation (if a nation of undead with vengeance on its mind tried to ally with you, would you spot-on trust them?). Plus, what you fail to notice is that the Horde is the instigator. At the Dalaran summons, though Varien did draw his weapon first, it was Garrosh who gave the first insult, then HE attacked Varien. The orcs have long has this attitude (and Thrall is definitely no exception) that they are entitled to a homeland on Azeroth WHEN THEY ARE THE INVADERS! And nobody give me that "They were manipulated" BS and look at the facts: many orcs realized that something was wrong when Ner'zhul said that the ancestors told them to kill the draenei (an event that got the whole snowball rolling) but they did anyway. Some, like Saurfang, are genuinely regretful of that mass genocide and are trying to make peace. I have to say I agree with the guy who wrote the first article in that Saurfang is a much better candidate for leadership of the Horde. Perhaps someone who saw the injustice and is genuinely sorry for it may better convince Varien of peace than a spineless political apologist like Thrall or a narrow-minded zealot with an UNJUSTIFIED (Varien's prejudices are justified) sense of bigotry like Garrosh.
On another point, you say that Varien has no true power of representation. I am sure that such actions would not be going on if the other members of the Alliance knew about this. However, it seems that they do know because they have voiced no objections to his actions.
So here are the points that I have made:
1. Sylvanas is perfectly aware and encourages the RAS's actions and manipulated Thrall to get Varien to be angry with him instead of her.
2. Thrall is not so much a Warchief than a spineless, incompetent, foolish, and apologetic politician.
3. The Horde are the instigators with a sense entitlement to the world they were marooned on.
4. Varien obviously does have the right to represent the Alliance because no one else has spoken against him.