Thanks for the feedback. obviously developer preview has still a few issues. There is a known issue where if you set the index ram quota larger than what’s available on the node, we may not be able to start the indexer on the node. I recommend using the following guidelines for now until we tune the product for compactness: http://docs.couchbase.com/4.0/getting-started/resource-reqs-dp.html
There is a known issue on the index fragmentation. It looks similar to this: https://issues.couchbase.com/browse/MB-14689 but I noted your condition as well there.
thanks
-cihan