It’s important to understand that this wasn’t really the fault of addon authors. This needed to be fixed because we were allowing something we really shouldn’t have. Many addons pull Inspect data when mousing over characters and there was nothing on our end to throttle the rate at which that data could be pulled. So if you’re standing in Dalaran with one of these mods and slide your mouse across the screen and over several characters within a very small amount of time, your client is spamming the database with Inspect queries. We’re correcting that issue on our end.

[...] We’re starting by capping the number of Inspects that can be sent in a 10-second time frame. It’ll likely be 5 Inspects, but that could change in either direction.

Keep in mind that this change is intended to help those using addons which are sending a lot of these requests from lagging or disconnecting. If you’re not actually using such addons, and therefore not sending a large number of queries to our database, the change won’t affect you either way. You’re not lagging or disconnecting because someone else in a raid or major city is unknowingly spamming such requests. (Source)

[...] I just wanted to reiterate that the original information on this change was meant to help add-on authors more than anything so that they could adjust accordingly. Unless the add-ons you use are requesting a lot of data, there isn’t going to be any particular change in regard to the amount of latency you might be experiencing in the game. (Source)