I think it is actually quite useful to have ALL the ColumnFamily metrics aggregated up to the keyspace level (and then up to the global level per CASSANDRA-7273). Much in the way that we have a complete set of metrics available at the StorageProxy level - including latencies - that are across all keyspaces and column families, these metrics are quite useful in general at the storage node level. In our case, we have a downstream monitoring cluster that we send metrics to. To build a generic, multi-tenant monitoring solution we have to either 1) aggregate all the CF metrics and present a "global" set of metrics or 2) capture metrics for ALL column families for all tenants. 2) is prohibitively expensive for us. Especially considering the small incremental benefit we see in practice from having this information broken down to the specific CF level. Almost always, we can diagnose issues with a global CF view of metrics. But going with solution 1), it is important that we get access to all the metrics.
The way I think of it, conceptually, you could have 3 complete and identical sets of metrics widgets instantiated: CF, Keyspace and Global. Every time something measurable happens, you adjust the corresponding metric widget at all 3 levels.
To be a bit clearer, this is more useful for data models and clusters where there are a very large amount of column families per keyspace (hundreds or thousands). Tracking only individual column families can be burdensome at that level.