I'm gonna say something unpopular: I don't like to rush.

[xxvaynxx]

Pulling 1 pack at a time is already tanking a dungeon.

And using Single target skills on a group of mobs is dpsing.
Just because you're holding aggro on 3 mobs doesn't mean you're playing it right. As a samurai I can tank 3 mobs while the healer heals me, says a lot about how useless a tank is if they pull that much doesn't it?

How are they supposed to learn without playing it tho?
Are you trying to help them or do you just complain?

I've had bad experiences where a Tank didn't speak English and was just running in the wrong direction fighting one mob at a time and we had to solo the dungeon without him, but it's extremely rare and an extreme example.
Most of the time people are willing and able to learn if you help them.
It takes time to grow confidence in yourself if you've never played Tank before and you're going through the process of level to 80, the dungeons do get harder and harder.
It's easy as someone who has been playing the game for years and have the power of hindsight but if you're new then you're unfamiliar with all of the dungeons.

Use common sense. If you're in like a level 15 dungeon sure that's fine.
But if you're in a lv80 dungeon or even level 50 and still don't know how to tank, maybe you shouldn't be tanking if you can handle large pulls and have to only pull each set of like what? 3 mobs? as that's the normal amount of each set of packs.