I was playing on molten two years ago for quite some time and I never had as drastic lag issues as I do now. They appear when (I play as rogue atm) you open with stealth-requiring skills, when there's massive damage being delt and when someone in party kills a mob. It is almost impossible for me to do anything in instance or group because my screen keeps freezing for 1 second every 2-3 seconds. I tried checking triple buffering and reduce input lag in video options to no result. And yes, my pc specs are more than enough to be able to run wow and my connection is really good and stable. Tried searching the Internet for possible solutions and nothing. I'm from middle-eastern European region if that may have something to do with this.
Honestly me personaly havent had any lag issues for some time on Lord, they used to occour when the realm was DDOSed other then that the realm never had any longtime lag issues as you describe, maybe its something related with your internet provider.