The frontal cone on nezir is killing people during the tankswaps at times, is it wise to run a third tank (so nezir is allways tanked) or is that just bad rng? We're not stupid enough not to stand behind the boss
During Sleet Storm we have 1 resto shaman, 1 holy pally, 1 disc priest and 1 holy priest healing on nezir. Boomkins and shadowpriests backing up in a DH/Tranq rotation. Think the main question in this is, do we make healing unneccesary hard by swapping dps from rohash to nezir early (after dealing with storm shield).
You absolutely should have two tanks devoted to dealing with Nezir and jumping to Anshal's platform just to reset debuffs. The tank damage on this platform is significant, your dps can't be getting hit by that breath, and the enrage should not be a concern.
You don't have much choice except to move your dps to Nezir once the shield is down. Otherwise you'll spend a lot of time stopping dps on Rohash to wait for Anshal to catch up and you'll be way behind on Nezir.
I think the rest of your problems usually stem from not swapping your healers around to the right place at the right time.
There's a few different things you can do with your healers to fix this and without seeing logs or having more detailed descriptions, it's hard for me to know what is best for your team. Initially I'd suggest having one of the healers on Anshal help with sleetstorm and having the resto druid taking hurricane go over to Nezir's platform until right before hurricane so his stacks can reset. If he can't for some reason, he needs to communicate and one of the other healers assigned to that platform has to come over from Nezir and take it instead.
To be more specific, I'll tell you what we did. We have a resto shaman dedicated to Anshal's platform; the only time he leaves is for the sleetstorm and he ports back over right after. We have three healers devoted to the Nezir tanks; a paladin is assigned to one tank and two other healers are assigned to the second (this has been several combinations - two priests, a priest and a paladin, a priest and a druid) We have three healers on Rohash's platform. Usually one comes over when the dps do (resto druid) and the other (priest) comes over right before the sleet storm. We also have a resto druid take hurricane most of the time with two rogues; if his stacks get high, he'll port over to Nezir to reset before the hurricane; he also sometimes calls for one of the other healers to swap with him if he doesn't have time to reset stacks. There needs to be some flexibility and coordination between your healers, as you can't always stick to the assigned plan.
Let me see if I can break it down for you in roughly chronological order, since it's a little complicated.
At the start: Nezir's platform has DK tank with two healers, Anshal's has MT, resto shaman, kiter, 6 dps, the other Nezir tank and his healer; Rohash's has three healers and 9 dps.
When the DK is about to get his third stack, our warrior and paladin port over. The DK and his healers go back to Anshal and reset.
Once the dps on Rohash break through the first shield, one healer and all of the dps port over to Nezir.
Once the DK's stacks reset, he and his two healers port back over. Around this time, the second healer on Rohash ports over to Nezir and the rogues go back to Rohash. Right after this, the resto shaman and all of Anshal's dps port over to Nezir with about 15-12 sec left before sleetstorm. The warrior and paladin port back to Anshal, usually with less than 5 sec on the channel.
So, for the first sleetstorm, we have a paladin, the second Nezir tank, the Anshal tank and the kiter on Anshal's platform. We have a resto druid and two rogues on Rohash's platform. Everyone else is on Nezir's - resto shaman, two priests, resto druid, paladin/priest/druid - whatever the seventh healer is.
Ranged dps and the resto shaman port back to Anshal's platform as soon as sleetstorm ends. Rohash's people wait until wind blast ends to go back. Paladin and warrior port back over to Nezir as soon as the resto shaman lands.
We essentially repeat this through three sleetstorms. The only major change for the second sleetstorm is that our paladin stays when the warrior goes back to reset stacks, bubbling off the stacks right around the time of the second sleetstorm and the priest stays with the Anshal tank during the second sleetstorm. We did this so we'd have the aura mastery on the second sleetstorm since the priest's barrier would be down, and so that the priest could use pain sup on the Anshal tank on the second channel because his own cds were down.
Also make sure that if you stack up for sleetstorm, people begin running out before it ends. The frost patch landing on top of your group will probably be a wipe if everyone's still stacked up.