1. CoordinatorWriteLatency is not available as a table metric until C*4 (see https://issues.apache.org/jira/browse/CASSANDRA-14232 and apache/cassandra@d38694a). And it's not included anyway in cassandra exporter.
2. At https://github.com/instaclustr/cassandra-exporter/blob/master/common/src/main/java/com/zegelin/cassandra/exporter/FactoriesSupplier.java#L202-L203 write is not included for null consistency. But in C*3 I only get null consistency, and as described above we don't have table metric to do a total on.

Fix:

1. Add CoordinatorWriteLatency, prepare for C*4.
2. Include write when consistency is null

I'll push a PR soon for this. I encountered another issue when testing with C*4