It is quite common to have a DCD in each datacentre and use zoning - you should send the BIG-IP logs to the closest DCD.
However, log destination failover is dealt with by BIG-IP ie use a pool to select the destination DCD.
Statistics failure is also dealt with by BIG-IP - the BIG-IP will send statistics to a backup DCD as configured in the same zone ( this is in AVR config )
So the DCDs act as backups in terms of failure, but it is not the case that all logs are replicated to all DCDs. If you send logs to a DCD and it fails, you have lost those logs unless you send the logs to two different DCDs using the BIG-IP publisher. Obviously that doubles the disk usage, network utilisation etc.