You're not doing anything wrong, per se, but as a healer main that has had everything stripped from them this expac (thanks SE, I hate pressing buttons in my video games. /s) I find I only have entertainment when I have a tank that pulls wall to wall and forces me to actually balance heals/dps. Of course, after being fed up with healers this expac, and SE's deafening silence over it, swapped over to MCH main, so as a DPS, doesn't bother me THAT much, but on dungeons I've done dozens of times, I'd rather it be over with quickly so I can get a move on and do other things.

However, if you're newer to tanking, or just not confidant, it's completely fine to take things slow until you can work your way up, improve, and do those big pulls.