If it is tied into world events somehow, the only plausible thing I can think of is that Uldah and I'm assuming everywhere else draws energy from Aetheryte crystals and if the energy they use is starting to be interrupted, depleted even from the Primals being on our plane, that would be the cause.

Honestly, going off that same thought, since the Primals are supposed to use so much of that type of energy to remain here. I would almost expect the wandering odin one they brought the concept art on to black out entire camp sites when its within proximity. But thats merely my speculation. Haven't noticed the lights flickering in Uldah or anywhere else myself.