Originally Posted by
bewbew
According to the mentioned leak, she now has powers she didn't possess before, and she probably knows everyone took a power-down after Legion and the loss of Artifacts. It's the best opportunity to be at war.
The book even says what she always wanted was Stormwind. We're only left to question "why".
Genn and Jaina both have a lot more reasons to want to siege Undercity than "Being abandoned in the Broken Shore". Specially Genn.
She personally led the assault on his homeland, and they were literally shut in ignoring the whole world.
That doesn't go away just because a big bad had to be dealt with. Plus, he knows of shady stuff in Stormheim (which is not, as some try to point, just "personal business". They are faction leaders, their attempts at power WILL include the Factions).
I'm not going by what is more "reasonable", and even if I did, I strongly disagree with what you consider reasonable, as I see no reason for anyone in the Alliance to ever let a Sylvannas' lead Horde to ever be left alone.
I'm going by what the leak pointed us. "Retaliation".
Book states she wants to attack Stormwind. That she always wanted to attack Stormwind.
Leak says she obtained a powerful thing from the Scar.
So she burns Teldrassil using this power, knowing she will be retaliated, and now she has a casus belli to be in war with the Alliance and attack Stormwind with the help of the Entire Horde, not only her own Navy.
In fact, consider this: The Cinematic shows us Taurens, Trolls and Orcs PREPARED to fight a Sieging army. If this was an initial, surprise attack, WHY WOULD THEY BE THERE?
There is absolutly no way she would have prepared warriors from all races in the blink of an eye to defend Undercity.
And these do not HANG in the Undercity. They only time they did was when Garrosh forced his Korkron to be the Undercity guards.
While we, the player, port around, in the story, armies have to take boats, zeppelins and other conventional ways of transportation.
Yet she moved an Army to defend Undercity across a continent.