Over on a separate thread in Elasticsearch I discussed and implemented 2 instances per node in my cluster, along with many of the other changes discussed here.
I also changed my logstash configuration so that all data is sent to a single ES instance, and that instance can then pass the data within the cluster. Rather than flooding all 8 instances (2 per node) with data, which resulted in overloading everything.
Its all stable and loading in data in the 12,000-15,000/s range.
Thanks for all of the help and guidance.