The truth is, some people operate at different speeds. When I first started tanking, sometimes I'd fumble around between pulls, struggling with target filters, trying to target the right enemy, or what have you. Sometimes I'd be on the wrong hotbar, go to shield lob, and end up face pulling, looking like a fool, because I rushed. If the tank isn't a streamlined work horse, pulling pack after pack, chances are there's a reason for that, and it's probably that they aren't comfortable with what they're doing. A DPS pulling a pack of mobs isn't going to make them more comfortable, in fact, it'll likely do the opposite.

Instead, the group can simply communicate:

"Hey, I'm not familiar with the layout here, can someone lead the way? I'll pull when we get there."

For the impatient DPS:

"No need to mark, we'll follow your lead" or,
"Leave the marking to me, I can do it quicker"