(Note: Somewhere during the thought process while typing this out my brain may have gone haywire and my sensibility drops like a rock, so excuse any part that may seem weird)
All You Can Eat:
With the failure at 5 stacks and 15s between tombs, I think setting up the two tanks on opposite side of her and near each iceblock location so the tanks have easier time reaching it could work better.
And uses 3 healers, in case the healers that was supposed to be on tank got hit by Unchained, then the reserve healer(who usually heals the raid) can take over for a shot while(the reserve healer will be hiding behind each block with the DPS unless called for, since he won't be healing tank), that or have the tank uses cooldown until Unchained is over.
Position
(Ideally, the healers won't get stacks this way, but let's presume there's some mis-position and healers can't always do it)Code:H R H 1 M 2 T S T
Basically, each time a frost tomb hit, the tank who's near that tomb go hide, and the other one taunt.
-Example: If the tomb is coming to position 1, then the tank on 2 side will taunt and Healer/Tank on side 1 will hide if they have stacks on them.
--The respective healer's position is a good condensing spot , since the healer should be a fair distance from the tomb's impact point, and the spot should be out of Sindra's LoS while the tomb's up.
All range DPS are to remains on boss while not hiding, and only enough melees to kill the tomb in 10s(but not too fast) remains on Tomb to kill it. This is to avoid the scenario where we kill the tomb too fast and nobody lost their stack at all.
The primary concern is that the first tomb. Because both tanks will have some stacks at this point.
What I 'think' will be done is this:
-Have Tank 2 tanking her at the start.
-Tank 1 wait behind where the tomb will be, so as soon as the LoS is up he'll be affected by it.
-As soon as Tank 1's stacks drop. He go into position and taunt off 2.
-Tank 2 hide behind the first Tomb until the 2nd BEACON comes, at which point he'll go hide at Tomb 2 position.
--As soon as Tank 2's stacks drop, the DPS can immediately kill the tomb regardless of if the 2nd beacon is coming.
-After Tomb 2 dies, Tank 2 taunt Sindra and Tank 1 go into position to hide.
Afterward, I think what will happen is something along this line:
-Frost Beacon comes up. Kull says which side is the marked person going to.
-The opposite side's tank taunt, the previous tank go into position to drop the buffet and remains there(to avoid tail smash/avoiding as many buffets as possible)
-Tomb hit, DPS hide for 4-5 seconds to let the debuff drops(You can move out as soon as you see 2-3s remaining on your debuff timer)
---Alternatively, the DPS group(the ones not on tomb) could hide every other tomb as well.
Repeat.