More info people can give the better in general.
Like what zones you’re encountering it in, what times, is it all the time or specific times, is it one character or multiple, etc.
One thing I would try is try a UI reset (I know Fryda has mentioned doing it a few times) and see if it persists with completely stock WoW. If it stops and doesn’t pop back up, it may be tied to an addon.
That being said, the number of reports on stuff along these lines makes me thing something else is at play but it couldn’t hurt to try.
I do also want to point attention to the US-server megathread regarding ability/loot lag in Tech Support and have people provide the requested info there if they think they’re affected by it.
The Oceanic one is linked earlier in the thread.