A few months ago I finally convinced my brother to respec his Arms/Fury hybrid nightmare into the more streamlined Arms/Prot hybrid from the sticky. I thought it would be a great "intro to tanking spec".
http://www.wowhead.com/?talent=LVMcbAbog0dbZVZcitoh0z
So far it has worked great and he has been much more effective as a main tank. We have recently hit 70 and have been looking into our specs in preparation of starting in on level 70 instances and eventually heriocs. I switched my Pally over to full Holy and have advised him that perhaps it's time to switch over his warrior to full Prot. To say he is hesitant would be an understatement. He really doesn't want to lose all of his Arms dps and talents.
It's his character, and I don't have the right to "force" him to respec. But we initially teamed up my pally and his warrior so that we would always have a tank and healer in instances.
Here is my question: How long can the spec I linked hope to main-tank? I think he will be fine for normal instances...but heriocs?
I actually hope I'm wrong and that his spec will work for Heriocs. Would save me the hassle of convincing him to respec again. (I'm still trying to get him to actually start collecting tanking gear instead of tossing +def stuff because it "doesn't have as much STR or crit".)