I'm a big Redis fan, but in this situation I would use Couchbase only.
Couchbase is rather efficient, and comparable to the performance of memcached when the working set of your data fits in memory. Most of the time, an extra caching layer on top of Couchbase is not useful.
That said, if you really need a caching layer, or simply some storage for temporary data, you can simply create a memcached bucket hosted in the Couchbase cluster. So you would have an "eventually persistent" bucket for your persistent data, and a memcached bucket for the temporary data.
The bucket types are described here:
http://docs.couchbase.com/couchbase-manual-2.5/cb-admin/#data-storage
In that context, adding Redis as a extra storage layer does not really make sense.