It is very difficult to convince your average player that they failed to react in time when every visual indicator on their screen is reinforcing the idea that they *did* react in time. The average player is not going to want to hear a lecture about castbars versus telegraphs, or theories on video/processor lag versus network latency - on their screen they see themselves clearing the AOE-warning makers before it vanishes and/or explodes, and a) it is a lie, and b) it is a lie they're buying into. To argue with them that they were "late" at that point is to basically tell them to stop trusting their own eyes and the information being displayed on their screen. It doesn't work.
I think you've become one of my favorite posters on these boards.

Given the overall quality of posts on these boards though, I have to admit that's not a difficult standard to achieve.