The lag actually double dips. An ability like WotL almost certainly is just cast at your character's current position, but if you've a running start you'll notice the AE is placed considerably far away from where you're if you started out moving at full speed. So this means your client is receiving the information late. All abilities basically have 2 times the lag factor subtracted from the time you're supposed to have, though the first half (the start) can be dealt with by memorization. That is, if you're running the whole time then you're already on your way getting out of the AE even though you can't actually see it.