I'm working the Proving Grounds now in PTR and I have to tell you, I am having the time of my life. I'm currently running the tanker scenarios and while Bronze wasn't bad (did get my heart pumping to be sure) the Silver is kicking my butt and that's okay. I'm one of those who like to kinetically work things out so out of every encounter, even if I fail, I learn something else to try.
I can't speak for others but when this hits live I'm going to be one very happy player.
You seem to learn like I do. I don't mind failing awhile so that I can refine things. The Proving Grounds is a great way to do that without wasting anyone else's time while you experiment and refine your skills.
To those who have tanked on the PTR, does it teach you how to work with a second tank?
The system is designed to just teach basics. It won't teach more advanced techniques as of this time. It's mostly focusing on learning how to get and keep aggro while protecting your healer. (As a healer I appreciate this lesson.)