http://ru.wowhead.com/spell=69409#english-comments
Catharsis 2010-05-14 (Обновление 3.3.3)
"too bad that nobody uses them anyway... :(" To suggest that no one uses DK tanks is absurd. I main tank LK for our guild in Phases 2 and 3. See, we DKs have this great thing called Anti-Magic Shell which will make the 50000 damage from Soul Reaper laughably less. Not to mention, with two damage-reduction trinkets and t10p4 combined, I have a total of about 8 cooldowns that I use in rotation for Soul Reapers, oRattja 2010-05-20 (Обновление 3.3.3)
It is, you can also reduce it with other abilities, like barkskin, shield wall or pain suppression. You can just "eat" the soul reaper and the after effect if you rotate your cooldowns. This is where we bear tanks with massive health really shine.utopus 2010-05-23 (Обновление 3.3.3)
the ability says that it deals SHADOW damage. Of course it will be partially resistible, assuming that you have GoTW or prayer of shadow protection etc.