Okay, this search term that led someone to my site CANNOT WAIT until Monday’s regular Q&A post.
“do i need defense to tank regular dungeons”
Yes. Let me say that again. Yes.
Granted, you’re not going to have much defense gear to tank Deadmines, but if you’re talking about regular dungeons from 70-80, or even 60-70, defense does matter.
Here’s the deal. If you want to tank, figure out what level the end boss is in the instance through WoWhead. Say you’re 74 and you want to tank regular Violet Hold. Well, Cyanigosa is level 77. You never want to tank mobs 4 or more levels above you, due to crushing blows becoming a possibility, but 3 levels is about average. So you can do VH at 74.
But what defense do you need? The number you are looking for, when you hover your mouse over your defense rating is the chance to not be hit/critically hit by 5.6% for a boss 3 levels higher than you, 5.4% for a boss 2 levels higher than you, 5.2% for a boss 1 level higher than you and 5.0% for a boss of your own level. This is because bosses (all mobs, really) have a base 5% chance to crit and this number increases by .2% for every level the creature has above you.
If you don’t have the required numbers mentioned above, try real hard not to go to an instance with mobs that are higher level than you.
The numbers at 80 are:
535 defense to be NOT critted by a boss 2 levels higher than you (heroics) and 540 defense to be NOT critted by a boss 3 levels higher than you (raid bosses).
If, of course, you are a druid with 3/3 Survival of the Fittest, you cannot be crit unless the mob is something like 5 levels above you, so you do not require any additional defense. You CAN, however, be crushed by mobs 4 or more levels above you, so stick to 3 or fewer levels of difference between you and the mobs you’re tanking.
It’s part of why I actually enjoy tanking on my druid. I know that as long as I go to a level-appropriate instance, I can’t get crit. :)