Red Ring of Death!

[Blarp]

You know, as much as you wanna claim white knight...people who say it's SE still to this day fail to explain why it happens to some and not for others - a broken game means it happens to everyone

There are videos with very clear proof of this type of AOE desync happening, yet the player does not appear to be lagging in any way.

http://www.youtube.com/watch?v=PGSnnof--LY

In that example, there is clearly no lag as the player is casting spells. One would think that if it were a problem with the player's network that every part of the game would lag including casting spells. As you can see, the player is casting a heal and it registers immediately after the progress bar reaches completion. If it were a lag problem as you and the OP seem to suggest, then one would expect there to be problems with everything else in the game including casted heals.