HDFS JMX dashboard metrics are missing.
Ambari is using wrong port due to HA properties that contain nameserviceId.
Default Ambari deploys contains old properties as well as new, so this Bug was not found in a non blueprint based HA deploys.
Workaround: Add the following property to hdfs-site in the blueprint: "dfs.namenode.http-address" : <namenode-hostname>:<http-port>
It doesn't matter which NN is used above since UI will get response with both JMX properties and choose Active one.