I have a very selfish plea for you. It won't cost you, I promise.
If you log in to panel.dreamhost.com, and go to home > suggestions, you get a list of submitted suggestions that you can spend 'credits' on. You should have 40 or so credits to throw around on these. Will you please, please, pretty please, spend 3 of your credits on Domains > Add Domain (you can use the filter to narrow down your search to just this category) - Allow bulk (batch) adding of domains.
If enough folks vote, it'll get some attention in their support queue an be implemented faster. :)
I have a billion zillion subdomains to deal with, and it would be SO nice to be able to add them in bulk instead of one at a time.
I have also added another suggestion, but it isn't up yet - it should show up in the Domains > Manage filter as "Allow bulk (batch) editing and management of domains. If you wouldn't mind throwing a vote to that when it's up, too, I'd be super, super grateful. :)