Thankyou for acknowledging this! The mirroring is functionally not a very useful HA/horizontal scale feature until this is sorted. Mnesia has the same problem, so one has to imagine that the root cause is Mnesia.
Running RabbitMQ in production for large scale OpenStack deployments, I have actually started to recommend a singleton RabbitMQ instance because the mirroring can cause all kinds of emergent behaviour during a network partition.
OTOH, RabbitMQ does handle OpenStack at scale very well when there are no partitions, which is no mean feat, so kudos and thankyou.