I have the exact same bug in wglDeleteContext.
In Catalyst 10.9 the call is slow (~10 sec) but bearable.
In Catalyst 10.10 and 10.11 the call does not stop.
Actually I created a website out of frustration to help my customers choosing a driver.
As you can see Google is a pretty good metrics to separate good drivers from terrible ones. As long as you refuse to acknoledge bugs (even with a basic answer to this thread) and don't put your bugtracker available with bugs YOU KNOW and we have to GUESS I'm gonna leave this site online.
I really like you AMD, more than NVIDIA and the stuff is definitely hard. But this fast release cycle is unfortunate.
This thread just came to my attention. I am the manager of the OpenGL driver team dealing with consumer OpenGL. We recently fixed a few bugs related to context deletion and I'd like to see if it solved your issue. If you'd be willing to share your application, I'd be happy to take a look at it.
You can contact me directly: my dot name at amd dot com