Thanks to my friend Robert I now grasped the concept of the VIP in RAC environments.
VIP's were created in order to speed up the process of letting the client know that the server died. Imagine that the server crashed without any possibility to inform the client. The client will then initiate a request and has to wait for the TCP timeout. That can easily be 120 seconds.
The client should therefore use the VIP in the tnsnames.ora. Performing a request now will immediately give a response.
The client can then initiate its TAF faster.