Countries don’t have a “Dark Heart” that they fight over but have absolutely no clue what it is, what it does, or how it could help them in any meaningful way lol.
Xal needs that Dark Heart.
“What’s it do?” 
“How can it help?”
“How does it achieve her goals?”
“What even are her goals?”
“Corruption of the Soul of Azeroth?”
“What’s the Soul of Azeroth?”