There's no need for tankxiety. Even if someone has 0 parctice. Just know your skills (you should read your tooltips from new skills you get). Don't use your deff CDs all at once and remeber that arm's lenght and reprisal are deff-cds too. Keep your gear up to date. The tanks have a single and an aoe rotation. All other stuff is dmg optimization. Don't be shy pulling wall to wall. If it fails - that's not the end of the world. Maybe check if the healer and DPS are aoeing if you're running out of CDs. You can communicate. If you warn your healer that you're just learning, they will maybe babysit you more.

Not using AOE skills is bad in my opinion. Even more if they are on someones hotbar and are just not used. But that's the thing in reading tooltips. Sure, they can be confusing. But if the person really cares, they would ask or check the internet. There are so many guides out there. Uuuhm ok, we're talking about lvl 80 characters. Uuuhhmmm maybe they really just don't care.

I'm just biting the bullet and go through the dungeon. If it was really bad, I'll blacklist the person. If I'm in a good mood, I'll try to teach or give some tips. But mostly I'm trying to give my best to speed the things up.