When SAS 9.2 was released one of the changes SAS made was to change the default setting for WRS from using a standard workspace server to a pooled workspace server.

This was to improve performance as pooled workspace servers remove the requirement for sas executables (sas.exe) to start and stop for each query, and therefore speeding up environments with lots of small queries.

SAS issued this tech support note:

Usage Note 39065: Documented best practices and other resources for improving the performance of SAS® Web Report Studio

Which outlines how to setup pooled workspace servers in SAS 9.1.

It also outlines a few other performance related changes you may want to try.