Varnish cache storage

First thing : you don't need to set a vcl_fetch rule if the condition depends on the request. Everything will be handled in vcl_recv.

vcl_fetch rules are only needed when condition depends on the server response.

HTTP Host being in the request...your vcl_fetch rule is actually useless.

Now that you don't need to tell "which domains should not be cached" twice, just use a single condition in vcl_recv like this :

sub vcl_recv {
    if (req.http.host == "domain1.com" || 
        req.http.host == "domain2.com") {
        return(pass);
    }
}

Note that you can also use regexp...not sure about which is the best...

So, in the VCL file, first simply define the backend with some name like this

 backend lorem {
  .host = "10.0.0.1";
  .port = "8088";
 }

Then define this in vcl_recv section

 if(req.http.host ~ "loren.com"){
      set req.backend = nginx;
      return(pass);
 }

This will send the all the traffic to loren.com (based on hostname) to the defined backend.

Define different back-ends for the different sites and it will work like a charm.