One thing I'd like to remind you, when we're talking about Guardians tanking Ra-den. Since both Savage Defense, Frenzied Regen and Tooth & Claw has a steep rage cost, it's not like we can just spam all 3 of them whenever we see fit. You can't just stand there and spam Frenzied to top yourself off non stop, cause then you won't have the rage to use Savage Defense before a Fatal Strike. Toot & Claw is a proc that is tied to Maul and Maul costs a ton of rage. So, you won't really be using T & C much outside of dps CD's like Berserk or Incarnation.
Also, Savage Defense is on a 3 charge system, meaning you can't have it up during the entire encounter.
The problem Guardians have with "tank -killer mechanics" is that Savage Defense isn't 100% guaranteed to dodge. Tortos Snapping Bite is a good example. We can have our Savage Defense active but if we don't dodge, we still take the full blow to the face.