I think that's responsible for the failure, but I don't believe that that's what's creating the outcry. In earlier times, most of the players claiming that raiding mechanics are too unforgiving were getting bounced out of Karazahn despite wearing sunwell level badge gear. Failure was the norm for them, it's what they expected. That hasn't changed. They failed at raiding in BC, and they're failing at raiding now.

What's got people up in arms is the fact that they now have expectations that are out of alignment with reality. Players spent the better part of an entire year raiding ICC10 with a 30% buff while wearing emblem gear that was 13 ilevels higher than the gear dropped in the instance. It was the equivalent of raiding Firelands on normal right now. They spent months running pugs with minimal standards and no voice com that would clear the entire instance because everyone overgeared it.

People got used to that, they expected that it was the norm, rather than a desperation pitch by Blizzard to bridge the gap to an expansion that was still a year away from a rushed release. When those expectations proved to be unfounded, they raged. If Cataclysm had been released six months earlier, this problem wouldn't exist.