I'm not an expert in equiping prot warriors by any stretch of the imagination. My prot warrior is only level 62 and has just recently finished all the Hellfire quests.
I ran one of the Hellfire Cit instances with a 61 fury warrior a few nights ago who seemed absolutely amazed that he had nearly 1500 more HP's than me. He asked me why he had so many more HP's if I was prot spec. I took a look at his gear and he seemed to really be focusing on stamina. I don't mean that he had a lot of stamina...I mean a lot of his equipment only had stamina on it. Here is his armory
http://www.wowarmory.com/character-sheet.xml?r=Lightbringer&n=Sonyador
I try to shoot for a decent amount of STA...but I also want to keep my STR, AGI, etc up as well. Here is my armory (it is showing some of my dps equipment still...like the boots, I have iron clompers with sta/def sockets for tanking).
http://www.wowarmory.com/character-sheet.xml?r=Lightbringer&n=Warbler
Am I missing something? Should I be trying to equip straight stamina for tanking? It seems that blocking, parrying, dodging, and being able to deal a decent hit to a mob is also important. I try to pickup STA gear when I can, should I make a massive increase in STA a priority?
On a side note: He was DW'ing in berserk stance and I was beating him on the damage meters while in defensive stance. I don't care about damage meters at all when I'm tanking, since my job is to distract mobs so others can dps. He was doing a good job in the group. But I thought it was odd that he wasn't crushing me in damage.