High Site Response Time

Y'all!

We have SharePoint 2010 farm with one WFE server, two APP servers, and SQL clustered. All Windows 2008 R2 and SQL 2008 R2. We also have Disk BLOB caching enabled on WFE server. After running some perf. monitoring tools we noticed thatSite Response Time is really high in upper 200ms. It stays above 200ms always.

WFE has 8GB RAM with 3.79GB utilized. CPU is below 3%. Any ideas?