That Y'shaarj thing got me thinking about one little thing: it's known that his remains, the Sha, fester on negative emotion, and at the same time, they act as a catalyst for them. One could say that Y'shaarj gifted the world with anger, violence, fear. But is this the only side of the medal?
As we know, Yogg-Saron was the Old God of death. He was the source of Curse of Flesh which converted Titans' constructs from mechanic to organics, turning them mortal, making them die over time to feed Yogg-Saron. But along with flesh and mortality, he gave them procreation, so that the process would turn into a cycle, a cycle of life and death, on which he could parasitize.
As Yogg-Saron made the form imperfect, Y'shaarj made mind irrational. What if Y'shaarj gave us all emotions? It makes sense - to make us capable of dying, Yogg-Saron had to make us capable of living first. So, to make us experience negative emotions, on which he could thrive, Y'shaarj had to make us capable to experience emotion at all. What if Old Gods actually made us truly alive? How plausible do you think it is?