Just a small correction (in fact two):
1. A group booking for whole 2A coach getting cancelled is a rare phenomenon and doesn't happen every day in every train , so people rushing to charts in this case is not unmanageable.
2. Irrespective of number of cancellation there is always a maximum count till which point WL can grow for a class and Quota, so at the time of charting only that many people(max count defined for WL) will rush to verify the charts.