In WCC some users can login and navigate quickly others see very slow performance.
It is always wise to review the WCC tuning recommendations. For 11.3.5 that information is in the WCC implementation guide.
But if the performance is only slow for some user(s) and not others then review the EEM configuration. Slowness has been seen when users are members of a large number of groups. If EEM is using an external source for users and groups such as Microsoft Active Directory one may need to define a custom mapping to reduce the number of users or groups EEM will see.
See Technical Document TEC586029 for details on EEM custom mapping.