I think your original network administrator was talking about optimizing the actual DNS lookup for your site. When someone first hits your site and if the DNS entry isn't already cached somewhere in the nameserver chain, it will have to do a full DNS lookup. The time to do this lookup can take extra time depending on how the nameservice is set up. That said, after it's looked up the first time and cached, any slowness is the result of some slow link in the route between the browser's machine and your DreamHost server (as you're currently investigating).
Here's the wikipedia entry on glue records.
As an example, here's what dnsstuff.com says about one of my .org addresses at DreamHost:
This was just as bad as this one for a ".us" address that is registered with another registrar but hosted at DreamHost:
Contrast this with a ".com" address of mine:
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