Hey Sachin,
Make sure when you are using the 'Audit Details' assertion, that you are leveraging the 'log' option and not the default 'audit' option within that assertion..... I've also personally seen better performance when that log sink has a larger file size configured, delaying the 'log rotation' from happening...
Can you post what your requirements are in regards to throughput and what you currently are getting now? This will give everyone an idea of what your goals are and how close we are to obtaining them..
thanks!