This discipline is pretty darn amazing. Far far far better than Exalted Mantle. It's 1/3rd the endurance and costs no end/tick. It has a lower mitigation effect, and wears off after mitigating less damage (which kinda washes if you think about it) *but* it also damages and stuns opponents who hit you *and* heals you. Think of this as a ward of tunare effect on steroids. And just like that spell, it's usefulness is greatest when fighting larger numbers of weaker mobs versus single tough mobs. And in those situations? It's an "I win" button. Seriously.
The other great thing about this (which isn't listed in the stats) is that it has an 8 minute refresh (compared to I think 15 minutes for the mantle line). The effect normally lasts 2 minutes, but with maxed extension (you have maxed extension, right?), it lasts just under 4 minutes (I think like 3:50 or so). Um... This means you can have this up about half of the time you are fighting.