There are multiple connections running at the same time when you play WoW. When this issue happens it means that your “world” connection has dropped, but your “home” connection remains connected. This post explains more about each connection:
Troubleshooting why your world connection (usually the one sending the most data) is dropping is what you should focus on. If it was caused by the patch then everyone would be experiencing it, and we’re not seeing anything like that. In most cases it ends up being a wi-fi, router issue, or ISP problem that causes the connection to drop out. Using a different connection may help avoid the problem if it is occurring along the route towards the server.