You couldn't of said that better. I fully agree with your comments! It compromise for the most part in trying to keep casual players well casual tanks and not wait till the next day in hopes of a tank. I don't think SE is in the middle they plan this out well. Forces people to go outside the box. Now this would be a major problem if you could only be one class and have to recreate a character just to remain relevant during gameplay. The best changes I can thinkn of adding content where all tanks can be relevant. One with dps checks another with a great need of defense, another with insane mechanics to keep you on your toes. That way all three tanks are utilized and no one get left behind.
