DNS resolution takes so little bandwidth (network/memory/cpu) the only realistic answer is misconfuguration of some kind.
That a video from a site took longer to load probably isn't a DNS issue, especially since your local DNS resolver keeps a cache of sites that have been resolved, and again, other than looking up the IP address, DNS has no other involvement with the network.
What you're describing is like saying the phone book made my phone call not go through. A phone book is a directory service (they used to call them Directories), DNS works exactly the same way - find the name in the directory, get their numerical address.
The actual connection is another thing altogether.