Well, there's 3 plate tanks that can get defense rating from every slot of gear, and then there's druids. Defense on any piece of leather creates a drop that only one 1/2 of 1 spec for one class wants. Other than Heavy Clefthoof, we got all our defense in TBC from rings/necks/cloaks/ a trinket and a weapon. Many druids also resorted to Resilience to be immune to critical hits.
Now, Blizzard can stack all the defense rating on plate gear and some tanking accessories and druids won't have to worry if an upgrade makes them vulnerable to critical hits. I had to sit on more than one avoidance/mitigation upgrade because it had dodge rating instead of defense, and I needed crit reduction somewhere else before I could change.