If you are getting Halfus to 25%, you are well past the difficult part of the encounter already... unless your DPS is on the wrong target completely.
Avoidance technically does help because it increases the time between stack applications, which is why the Nether Scion's debuff of adding 25% chance to miss is so crucial when Nether Scion and Slate Dragon are both present. If the boss doesn't connect with his swing, the debuff is not applied.
Mitigation helps reduce incoming damage, but it makes no difference if that damage is still greater than the person can be healed through while they have the debuff. If a healer can only heal you for 5k HPS cause of a debuff, if you're taking 10k DPS in damage (even if mitigated down from 13k DPS), it is still more damage than can be healed.
The mortal debuff is a physical debuff so any physical immunity will remove it including Iceblock, Divine Shield, and Hand of Protection. If the tank uses Divine Shield or receives a Hand of Protection from some other paladin, they should cancel it immediately so they can begin tanking again. Many tanks may have macros like this for such an occassion.
If you're swaping every 5 stacks, you're probably swaping too often and not letting it fall off the other tank, resulting in two people being high in stacks and unhealable.
/cancelaura Hand of Protection
Again, a key concept of the debuff is if he can't hit you, it isn't applied. Since you aren't releasing Storm right away, you can't interrupt the Shadow Nova even if you wanted to. With this in mind, you can actually extend the duration a single tank holds the boss by kiting him more. Mobility effects such as Intervene and Heroic Leap to get away from the boss can slow the rate of incoming stacks. Additionally you can have your tanks swap by taunting from range so the boss has to run over to the new tank before starting to apply the debuff. Once interrupting the Shadow Nova becomes a priority however, you will not want to be kiting him unless you can have a ranged DPS like an Elemental Shaman reliably interrupting for you.
For my 10 man we have the benefit of a protection paladin and a holy paladin so have the benefit of two stack drops. We have one tank handle the boss to like 10-12 stacks, get a Hand of Protection and start tanking again. By the time he starts building up again we are on the second drake. The other tank takes over on the boss and does similar, tanking relatively high in stacks then sheding them with a Hand of Protection and then tanking the rest of the way until the second drake is dead. Generally speaking in combinations that involve Slate Dragon we don't bother killing him at all so at this point it is just trading back and forth the boss whenever your debuffs fall off.
Last edited by Quinafoi; 04-07-2011 at 12:22 PM.
"In anything, if you want to go from just a beginner to a pro, you need a montage." /w TankSpot WTB Montage for Raiders.