The lag is deliberate which is why this issue is depressing. It's not like SE is just using cheap hardware that randomly lags, or that their servers are in Antarctica so everyone has poor ping to it. The game chooses to do most thing on server side and the price you pay is lag, and in this case crippling lag. The problem is that on an ability like WotL, if you move the moment you saw the ability, you'll get out of it with at most 0.5s to spare. Assuming WotL is 2.0s cast, that's 25% on cast bar left, which is actually a pretty reasonable time to escape an AE. However, now add in 0.3s of lag (possibly more), and your margin of error is way smaller than what you think you have. Basically the last 20% of the cast bar might not really be there depending on lag, and that's what frustrates people because you can't rely on your screen to be accurate.