Yes, WebDAV will max your local connection. Its generally not the encryption that makes ssh slow but the fact that it is designed to give real time terminal feedback. In order for you to see each letter typed in an ssh session, the buffers are really small and it intentionally sends a tone of small packets. Great for single characters bad for large file transfer.

Its OK here and then when you need to push a config file or something but moving large files is not really what its designed for and consequently, it sucks.