Performance issue Struts 2 Tag

There is huge performance issue and CPU hogging with Struts2 tag , this was observed while rendering JSP. These are some performance results obtained

Strut 2 Tag - With all performance tuning applied as per Struts 2 documentation - Freemarker caching etc...
Load Runner Tool
40 users
900 hits per second
10 transaction per second

Results
CPU utilization 90%
Response 3.5 sec

Replaced some of Struts2 Tag , with Custom JSP Tags like (s:label, s:text,s:textfield,s:hidden,s:param)
40 users
900 hits per second
15 transaction per second

Results
CPU utilization 70%
Response 2.0 sec

Some where down the line Struts 2 tag are very cpu hungry , to people to adopt to strut2 framework cpu utilization should be optimized .