My GLD is 21 and I have done a bunch of Satasha, Tam-Tara, and Copperbell from 15-21. Its pretty sweet to go in as a tank and take charge and set the pace, and basically "teach" some new players. Pull at a steady pace, mark targets, keep hate, explain the bosses and more often than not, people will tell you how great this run was. When or if they get a bad tank, they will realize it immediately. I'll give pointers too, but always politely and never condescendingly. It can make a huge difference in how they react, and may impact their decision to keep playing.