Originally Posted by
Nathanyel
Void Lord: "YOU CANNOT DEFEAT ME!"
Medivh/Adventurers: "I know. *pants* But he can."
(Illidan already has strong parallels to MCU Loki, so him freeing Sargeras to this effect would work perfectly)
Maybe just a silly theory, but what if that's why Xal has been absorbing various energies into the Dark Heart? Building up an equilibrium of all 6 forces, then expunging the Arcane of Dalaran (and likely other sources), which creates a "vaccum", for lack of a better word, that sucks out (enough of) Azeroth's Order.
I'm still assuming "Dimensius" IS K'aresh's Worldsoul. It tilted towards Void maybe due to early influence of the Ethereum, which then attracted alien Void forces, which the Ethereals believed to be the cause of Void activities on their world.
The planet breaking was then Dimensius being born, which may have only been a couple hundred years or so ago, explaining why the existence of a Void Worldsoul hasn't been as catastrophic (yet) as Sargeras rightfully assumed.
Maybe he felt the rising influence of the Void on Reality, but attributed it to Azeroth, which then prompted the repeated assaults in "recent" years, beginning with the relatively haphazard invasion of the Orcs as grunts to soften Azeroth's defenses.