Guess i just haven't done enough 'good' guild runs
ZA is a bit of an anomaly.
I've found many people struggle with it and I have a few theories why they do.
The difficulty level from Bear to Zuljin changes dramatically. People don't expect it to get so much harder as quickly as it does and as a result they underestimate the place.
Because they underestimate they don't take it as seriously as a 25man raid so they don't see the point in Flasking and so forth like they would normally.
The guild I mentioned have a 4 chest team setup and organised just for trying to get timed chests.
They only take the really good raiders and everyone knows exactly what they need to do.
All it takes is one mistake or one person who doesn't know his role 100% to kill your chest hopes.