An unfortunate effect of the "Great Airline Consolidation" is that the airlines have greatly down-gauged their capacities. I remember an experience I had with a disruption on the old Northwest airlines due to a cancellation. NW used to have 8 mainline flights a day non-stop from DTW to Green Bay thus allowing easy re-accommodation, now Delta has 3 and 2 of these are smaller partner flights.
The Over-sales CFR refers to delays of 2 and 4 hours, which unfortunately has become a bit of a joke. More common are longer delays such as the 22 hours which Dr. Dao was quoted for re-accommodation which IMO is simply unacceptable.