I know what you are going through, last year, I was you. Take this advice mate, let them die. I know, people are going to whine and get angry at me, but doing a dungeon run is a group content and as a group we need to work toghter. If a tank does not wait and just rushes, I ask him in a nice manner to wait and let me buff up the group, if I am inexperienced with healing, I let the group know this. If the tank still rushes and does not listen to a single word, I just do my best and if he dies, he dies.

Tell each tank that you are learning and that they should wait for you to buff them, if they run ahead going LEEROY, what happens next is their fault. If you think tank is making you do extra stuff by rushing, let him know that he/she needs to slow down, if they dont, let them die.

Your 3 steps are good and I would stick with them.