DNS sever performs a conversion from Doman name (i.e. Bitcointalk or any human readable URL) into IP address. this process also known as address translation.
so its not a a part of internet connection and there they dont see your recovery seed. Also, with the exception of the web wallet, the seeds are encrypted in a file, and then you need a password to decrypt that encryption, while the hacker needs both the file and the password, and therefore there is no logical reason for you to enter your wallet seeds in an online device.