So then am I trying? Or am I being lazy? Furthermore, who should be the one to decide? Myself? Or the other players?

I believe the ideal situation would be for anybody that is new to be able to try and fail without risk if being kicked/beat down for that as well. It's something that takes cooperation and input on both ends, I believe, just like any learning experience. You have to be pushed a little, and the ones teaching have to know when to stop pushing and let you grow strong enough for the next push.

I do know one thing though, and that's that I always received the most positive feedback when I played how I was comfortable doing so (some days DPS'ing to help, others healing only because the DPS were reliable with their damage). I ran Halatali again today with a player new to tanking and a mage with green leaves, and the tank had no idea what he was doing whatsoever. I've never tanked before but I explained to him that he needed to pay close attention to the icons indicating his aggro level with adds, that he needed to not focus only on one add and let the DPS take care of the killing, and that he needed to use abilities such as Flash to keep aggro. After I explained that, he did great and and we cleared with no further issues.

I could have told him to keep the aggro on him and stop being worthless, and I could have told the newbie to vote-kick him so that we could beat the dungeon easier. I did not, though, and we got through quite alright. I like to think as he gets further along, other tanks with much more experience than myself will be welcoming to him in an area he is still growing comfortable with. Certainly a blunt kick would have helped no one.