I've beaten all three extreme primals several times; not saying this to brag, but to help substantiate the point that I typically have no lag issues and often participate in high level events requiring quick mobility. For the past week I have been getting these intermittent periods where the game just stops for 1-3 seconds. My character can move, but everything else is frozen in time. The game then catches up with everything moving at hyper speed. I have still managed to do Titan Extreme with this issue, but it is OBSCENELY difficult as I have to base my movement for plumes and landslide by effectively counting the delay in my head and moving. Double plumes in the last phase is really exciting...

Sounds like others are having the same issue. It was especially bad this weekend which leads me to believe it may be based on server load, but not sure.