Cannot import Soapui plugin in Eclipse
You already aware that update site is not working.
So provided an alternate way, you need to manually install the plugin. Check here how to install eclipse plugin manually.
Sorry if this does not work for you.
You can download plugin from http://sourceforge.net/projects/soapui/files/soapui-eclipse-plugin/domyessay.today
This little older version.
I've been also looking for the guides how to import the plugin in Eclipse.
In case someone needs this infor as well, the download moved to this page: https://www.soapui.org/downloads/soapui/source-forge.html