I am also experiencing issues with multi-site PSC deployment in my vSphere lab.
When connectivity between sites is OK Web Client works about as good as it can, but when either of sites go down browsing remaining vCenter Server with Web Client becomes horribly slow and often just result in timeout error.
It seems that Web Client cannot handle any connectivity issues between multiple vCenter Servers in multi-site deployment. This is very serious issue as one of use-cases for multi-site PSC deployment is with SRM, but it seems that if you lose your primary site you also lose management capabilities of your DR site!