Every day since Remix launched, I’ve tried to do some stuff in Suramar. Every day, I’ve been met with literally unplayable lag. I mean the kind of lag I’ve never dealt with before. 10-20 full seconds between actions. And I know I’m not the only one dealing with this.
I’ve been sticking to non-heroic mode to do the story and had no lag issues over the whole weekend all over, including Suramar, so that may help.
Otherwise, not much that can be done other than wait out the initial hype.