Aww... :( I don't agree with just booting someone for something like that (I generally don't boot, period). How are people supposed to learn? I work on a lot of stuff solo on my bear, but it's a totally different ballgame with other players around grabbing aggro and Repulsing/Firestorming things out of position. That might be a thought, tho (and I've done this a bit with friends)--baby (or "baby") chars, each of us doing one we don't normally do. Me on bear for example and a bear friend playing bird. They teach me about being a bear while I give them tips on birding. We go through the level really slow, pausing after each mob if possible and talking about how to do things or how to do them better. Add Rauen and Griev, CSB. I promise I won't boot you if there's an oops.
ETA: And yeah. Tanking well is really, really hard. Hat's off and many, many thanks to all the good tanks out there!