Druid and Maul

Why does the Maul ability for bear take a few seconds to actually Maul when all the other abilities are instant?
I’ll be clicking on Maul and my bear will just stand there but if I get tired of waiting on Maul to actually work and hit Swipe, it will swipe instantly!!! I have to have taunt on CD because the DPS will pull aggro while I’m sitting there waiting for Maul to activate after clicking on it 50 times, and yes, I have the rage for it. Is this a bug?