We would also need a test wherein each thread does both a CRUD operation and a Query - possibly verifying the CRUD operation was applied - just to make sure we're not taking advantage of caches and say and immutable Lucene index for the Query-only tests.
You can make each of these tests multithreaded too but I would keep them separate, or at least have to option to run the same test configured to run in a sequential single-threaded loop as you would be looking at it in a different way for diagnostics.