In 2.0 Blizz changed a few things with casting and latency (mainly because people where complaining about people that use quartz).

Quartz still shows the latency, however, you no longer have to do /stopcasting, just spam the button. The server will cast again as soon as the previous spell is finished.... The server also queues for about 1/4 sec. You do not need quartz for this... quartz just makes it so you don't have to pound your keyboard into the ground.