Everytime there is a call to the oVirt/RHEV, the full authentication against it is performed,
which has quite a big overhead (for more details http://www.ovirt.org/Features/RESTSessionManagement)

Since oVirt 3.1, there was added a support for getting a session token
and authenticating with it, which should be much faster.

At least in my setup, with remote RHEV authenticated over LDAP,
the response times are very unpleasant.