I play on Outland EU. World lag has existed since launch, it's less on certain times, more on other times. Before 8.1 the world lag was mostly on certain zones, like Drustvar being the worst case scenario. After 8.1 every zone has serious delays for character actions, specially the Alliance zones. Horde zones don't lag as much. Outland EU is like 90% alliance too. Warmode OFF lags the most, Warmode ON lags, but not as much.
Sometimes on evenings Boralus is like a broken chinese mmo game.... Everyone complains about that in Outland, yes people are complaining in yell Chat, in general and trade, also guildies complain about world lag, so I am not the only one. The only one who does not know about it, seems to be Blizzard themselves.
Dungeons, Raids, Battlegrounds and other instanced content that have their own servers work good. Only World server seems to be lagging.