Originally Posted by
Shizari
Also outing myself as an Alliance fanboy here, but I have knowledge of the lore to back me up. Not perfect memory, mind, but still.
Sylvanas in the past was twisted by Arthas and the scourge, becoming a creature of vengeance and hatred that only cared for her own survival above even her own "people". Her original goals mostly revolved around securing a foothold for the Forsaken, in order to build them into a weapon against Arthas. For the most part, she succeeded.
And then the Wrathgate happened. Most of the Alliance and Horde knew there some crazy stuff going on beneath Lordaeron's former capital, but they were given a first hand lesson in just how far she went. Although it was traitors working with the Burning Legion (who Varimathras revealed to never actually stop being a part of), everyone knew that it was still Sylvanas-sanctioned experiments that lead to it.
Come Cataclysm and the final defeat of Arthas, Sylvanas wanted to strengthen her hold on Forsaken land, no longer seeing them as just tools, but rather people she's saving from the same hell she saw after throwing herself off the Frozen Throne. Unfortunately, this new mentality, and the reveal that she had those weapons, changed her. She believed that all of Lordaeron the continent should be hers. And so she set out. She was probably always planning an invasion on Gilneas, but the orders from Warchief Inconsistent provided a nice cover. But even then, she denied orders to use a weaker strain of Plague, and used the full on Wrathgate brew. This turned Gilneas into, as one poster here described "a Fallout 4 wasteland". She set her sights on Ararhi, expanded into the Hinterlands, and completely took over Hillsbrad by Plague-nuking Southshore and turning Hillsbrad Fields into a science lab. Not even neutral factions are safe, if her ruthless expansion into the Plaguelands and her capturing of an Ebon Blade member are any indication.
In nearly every military campaign Sylvanas launches, her plague comes with her. There's always plague carriers, even now in Legion's Dalaran (which, btw, made me burst out laughing when I saw). Maybe having no to lead the Horde against the Legion will change her for the better, but the fact of the matter is the Horde is still being lead by someone who has no issues with collateral damage in her campaigns and is probably one setback away from going completely Lich King 2.0 on the world.
I'm excited to see the new faction war between Zombies and Werewolves!