Decimating Strike is a 90% healing reduction debuff equal to the duration of his swing timer. Switching tanks won't help if you get hit twice in a row because even a Paladin's Lay on Hands is completely worthless, only the healers can actually provide significant healing.
Why are you using a single tank strategy on normal mode. While this may be what some heroic mode groups use in order to get sufficient DPS to kill the boss in time, it isn't necessary in normal mode and you make things harder for your healers than it has to be.
Each shard does 25 stacks. If you swap at 9, then you would end up with 9A, 9B, 7C ... 9D, 9E, 7A ... 9B, 9C, 7D ...
This rotation results in a different combination of DPS taking each shard. Additionally, it has the person that started one shard being the person which ends the next shard. This is not significant amount of time for their damage reduction cooldowns to become available again. Also, since you are only going to 9 or 7 stacks, healers will only gain 1-3 applications of Vital Spark per heal and the vast majority of that would be less than 3. You greatly hinder the rate which your healers gain stacks and are thus which is the exact opposite of what is necessary in a single tank strategy, in fact a single tank strategy is actually more likely to stack classes which tank take full shards (Shadow Priests in particular) in order to maximize the amount of stacks of Vital Spark healers gain. If I were to burn all of my mana casting as GCD locked I would gain around 39 stacks maximum using a method like this. Splitting it 13 and 12 I would gain around 56. Having a DPS like a Shadow Priest take the entire Shard I would end up with well over 100. I can only afford to do a hard burn of mana once a fight, if I heal efficiently I would get no where near these numbers. Every 20 applications of Vital Spark is an additional 100% healing done to the tank when converted to Vital Flame. So splitting a shard in half almost adds an additional 100% healing over splitting it in thirds.
When it is all said and done, it doesn't matter what tank you use. If they are hit two times in a row, the tank can do nothing about that, only healers can.
Your strategy as you have approached it is not viable. Healers will never be able to have sufficient stacks of Vital Spark to properly execute a single tank strategy. The one thing necessary to a single tank strategy you are also trying to reduce which makes it completely unviable.
1. Switch to a two tank strategy. If you reduce the total health of your Decimation Blade tank then healers require less stacks of Vital Spark to heal them. This allows you the ability to split shards more frequently or always.
2. Since shards stack to 25, you want to split them in half with the DPS which can survive better going first. The first person goes to at least 13 (more than half). Ideally you'd like the first to go to 15 because that is one step higher (every 3 stacks means it generates more stacks of Vital Spark for the healers) though it isn't absolutely necessary. Hunters, Shaman, Rogues, and Mages you typically want to either not use (have as a fifth person backup) or as second in the rotation (taking fewer stacks). Other classes will generally have some form of mitigation and would work at reducing the magic damage with Shadow Priest being the most extreme case.
3. Work on your healing assignments to maximize stack gains.
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Originally Posted by Quinafoi
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