Queue time is dependent on number of players queued. Queues were faster in MoP because you had several times the number of people needed to get a single game to pop, in the queue at any given time.
Now, you have barely enough players in the queue to get a game to pop. That's why there's a 25 minute queue. It's the same thing we experience in XP off brackets on scheduled game nights. You have just enough people in queue for a game to pop, the game happens, and then the few people who queue during that game have to wait until the next game starts (~25 mins).