I think it is ridiculous that a DH tech emails me back that they don’t support the Multi-site stuff… really dont understand mirroring… It took me hours of understanding and fiddling to make this work - no thanks to DH
Here goes multi-site set up using mirroring… on shared server
Read this light version description:
You will need this plugin also:
and this walkthrough:
Where WP Multisite uses real domains not folders to generate (clone) the new site. On shared server (can’t use wildcard)
 You set up a domain from a client say on Go-daddy, they point to NS1.dreamhost or whatever the domain is on DH.
 You create a subdomain on Dreamhost and the domain your client is pointing to DH servers.
 You make sure the subdomain is using the ROOT of the multisite domain instead of its own natural folder for information when setting it up in DH panel
 You mirror the new domain to the subdomain
 You use the Wordpress Domain Manager plugin to set up the sites on WP
 You fiddle with it for about 3 hours… just kdding, wait until the dns propogates… flush your dns and all the directions on the link I listed at the top