Let me just start by saying that i play on a potato laptop. Before the patch update for 8.1 i had no issues raiding/anything else on completely low settings. After patch update i noticed server input/graphics lag. This was happening anytime the WoW game screen was open but not when it wasnt. Discord voice was also being affected. After many hours of cleaning caches, checking memory usage, settings, disk defrags, driver updates, still there was no change. After consulting an in game guildy i screenshared and we found something very interesting. One thing was off. Blizzards auto-detect graphics card setting was choosing the unused crappy onboard graphics card instead of the second one installed in this particular laptop for gaming. Immediately upon switching this setting the lag/delays on everything cleared up to the original feel. I just wanted to write this up just in case any other potato users found the same issue as i did. I would highly recommend checking this setting before doing anything drastic like reinstalling. And remember i am using a laptop so i doubt this will be effective for a desktop pc. Hope this helps anyone frustrated. For The Hordeeeeeeee!!!
Have you tried disabling addons and/or doing a full UI reset? Weak Auras 2 was causing my (and others’) frame rate to drop considerably.