Nice guide. One thing I would like to point out is that, at least when I ran the instance last night at least, the drain life is in fact able to be interrupted. I think your group composition just wasn't too great for it, as I believe the mage is the only one that could interrupt it on a long cooldown.
Great job explaining everything, trash and bosses. The group I was with completely skipped the Brann Bronzebeard boss area, and this video definitely is wanting me to run it again!