AMZ is the best utility an Unholy DK brings to a raid, and is alone a good enough reason not spec Frost. When used correctly, this will be your raid's strongest defensive CD. Do not be fooled by the tooltip to think it will only absorb the stated amount of damage. In reality, it will first absorb 75% of the next magical attack, and only THEN, if the amount absorbed exceeded the stated amount, it will vanish. Therefore, it works best when soaking single high-dmg attacks, and fails miserably soaking multiple low-dmg attacks. For example, total damage absorbed by an AMZ covering 25 raid members can easily exceed 1,000,000 (vs Majordomo's Flame Scythe, Rhyolith's Concussive Stomp). Fortunately, there are many useful chances to use it in Firelands, when timed correctly. Some were already mentioned, and others will be mentioned below. Precise timing is an issue when other low dmg magic attacks risk breaking the AMZ before the big dmg hits. Note also that dmg taken from a shaman's "Spirit Link Totem" is absorbed by the AMZ and can break it, and so the two should not be used together. Personally, i keep Blood Tap ready for fights requiring precise timing for AMZ. It's worth it. Also, try to use AMS separately from AMZ, for maximum total dmg reduction.