There are at least three distinct and separate things that you might feel are lag:
- FPS. This is what you are talking about, and it is very real. I was playing on a “potato” - which was a perfectly fine PC, suitable for crunching lotsa numbers in R and Mathematica and big spreadsheets - in Legion and 8.0. The increasing graphic requirements in BfA - which I personally regard as worse than useless - forced me to replace it, which cost me more than many years of playing WoW.
This one is all about how many pixels are on your screen, and how fast they can be shuffled around. It’s about load on your CPU and GPU. Every time the anointed arrogant artists feel their masterpieces deserve more attention, and they deserve more of your money to be sacrificed for nothing, poured down the endless maw of Intel and Nvidia, they increase the load of graphics your PC has to cater for.
You can mitigate their megalomania by reducing your graphics settings, reducing your Resolution Scale in System settings, and even tweaking some settings to lower than standard as described in this thread: Graphics macros for better fps (Updating for new forums)
- Server Lag. Server Lag happens when Blizzard’s server is not processing events fast enough. I see this sometimes on large realms - the classic sign is when you click on an NPC or postbox and it takes a second or two to respond. It can have seriously trippy effects in combat situations. Seen at the start of pulls in raids, where Server Lag and FPS instability often combine, and often in Assault conditions in the world - sometimes World Bosses, in the days when a lot of people did them.
Here’s a recent video explaining one hypothesis about the rapid increase in Server Lag in BfA:
There is nothing at all you can do about server lag other than endure it.
- Network Lag. This is when the routers between you and Blizzard are not working well, perhaps losing packets that have to be retransmitted. You can see a rough estimate of this as “Latency” when you hover your mouse oner the red questionmatk for Help on your bottom bar.
It is possible that network lag can be in your house, especially if you’re using wifi, or sharing your connection with others, but I find mostly it’s a matter that the ISPs will get around to sorting out.
