Considering you have about 57 VMs per host, the resources may not be overloaded but it is possible that a VM will need to wait for scheduling time, hence your CPU Ready percentage. A good resource for helping troubleshoot CPU Ready is esxtop. Check out Duncan's site: http://www.yellow-bricks.com/esxtop/
Message was edited by: jamesbowling
Just because CPU usage is "low" doesn't mean CPU requests are low. Its context switching basically. Even if each guest only uses bursts of 1GHz for a second or two, if most are doing it constantly you are going to see CPU Ready Times.
You really need to watch ESXTOP or batch mode output to get a much more granular (albiet 2s interval) view of what VMs are doing. vCenters "Real Time" isn't exactly Real Time but generally its good enough. However in unique situations like this it can be difficult to see that indeed you have overloaded your CPUs.