I have the same issue as OP.
When I visit the main page: www.wowhead.com I get a semi working version, it shows pictures and html but seems to lack functionality.
Basically I can't search or find anything.
It works when I'm home but not at work. There are no restrictions in our firewall or anything.
I have tried three different browsers, reinstalled java, also it's the same issue for my colleague.
Any help is appreciated,