Didn't you post this on Flames too?
Reminds me of the build I currently run for instance tanking. However a couple pointers.
Don't tank in Defensive. Tank in Offensive. Ditch the AAs you have in Defensive Stance, move them elsewhere. You don't need them at all for instances. Level 90 Legendary gear is more than sufficient where you don't need to go defensive at all, and you don't need a shield very often either (as long as your healers don't suck).
Ditch the AGI line as it's pretty useless. We have plenty of AoE abilities even prior to getting our Epic: Rampage, Open Wounds, Bloodbath, Berserker Onslaught, Insolence, Enrage, Stunning Roar, and once you get the AAs, Dragoon Spin and Jeering Onslaught (Jeering will become one of your most used CAs).
You're missing the single most important AAs to a berserker: Relentless Assault (an absolute must have), Enhance: Berserk Rage, Enhance: War Cry, Enhance: Juggernaut, clicky Berserk, and entire Cyclones line. Those should be your number one priority before considering anything else.
All the defense in the world means diddly if you aren't holding aggro.
Remember to adorn your stuff. Ethereal Adornments of Endurance (Superior) for Wrists, Ears, Helmet, and Gloves goes a LONG way (about 1800 HP or so). Remember to spec in your character development for +Max HP and +Physical Mitigation.