If you like tanking like you say you do, you have to toughen yourself up to people testing you in dungeons when you run. It's our community and this is why we have such a severe tank shortage. All these negative experiences can do is help you to grow from them and become a better tank and harden your in game character. Keep your confidence, though. I remember my first dungeons, especially as a gladiator and I had the same things happen to me. It's almost like a hazing ritual for new tanks. You can let dps keep pulling and watch them kite, get healed, or not get healed and die. It's up to you. If leveling your tank is stressful for you, try leveling with a friend if you can. It helped me a lot. Good luck!