The funny thing is that how fast you run a dungeon is more about a healer than a tank.
Yeah the tank is the one pulling and getting all the aggro but at the end of the day it's about how much the healer is comfortable at healing it all.
Wanting to get the most mob you can is not only faster but challenging. I mean, there is no reason you wouldn't want to pull more unless the healer can't keep up.
If you as a tank don't feel safe to do it, that's ok, but don't be so hard on yourself and try things.

It's so fun when I get a healer that says "pull them all" and I do it even when it looks like we can't survive it.