Same thing happens to me... but it started today, like few hours ago... it was working earlier today.
When I click on "wait list" it doesn't go to "pending" instead nothing happens... but I noticed that if i wait some time (like 2 minutes), sometimes it turns to "pending" (sometimes nothing happens at all) like if there was a delay. Might it have to do with Blizzard problems with connections they are having right now in Europe? Thanks!
 

I think my OQ bugged somehow. Today I got the "battletag missing" error on my warlock (my mage and priest worked fine), to fix that i did an /oq harddrop followed by a /reload ui. But now I cant seem to join any OQ raid... when I click on "wait list" instead of going immediately to "pending" nothing happens... it's just stuck like that. It doesn't seem to be a communication problem because when I try to join a password protected raid it does ask me for the password.

Could it have to do with the numer of people in friends list? Earlier today I got several wow error messages saying "you have reached the cap before the cap" and i think it started removing randomly friends from my list... 

Any idea what it could be? thanks in advance.