Automation being king, this will do it. The general process for each host:
- Set the syslog destination
- Insure a firewall exception
- Restart the syslog service.
In vSphere 5.1 the Set-VMHostSysLogServer cmdlet was added to PowerCLI. While there are other ways to accomplish the same task, I tend to prefer using any method that is more obvious when coding. Set-VMHostSysLogServer it is.