We currently run with 2 healers and 3 tanks, 2 tanks - 1 healer in the throne room, our only issue is with the throne room. Outside team are fine.
Inside we have a Paladin healer with Warrior and Monk tank inside.
My main question is for healers inside is how do you manage the toxic mist dot and then the volcanic ash damage?
We have been theory crafting for our paladin healer for the next reset and we believe that he could either take option
1) Hand of Purity and weave that into just before volcanic ash explodes
2) Spec into Unbreakable Spirit and use Divine Protection just before volcanic ash explodes - which we feel may be better option.
Would love to hear about how healers manage with the haroom team and what abilities or tips they use on the toxic mist / Volcanic ash combo as may need to rotate our resto druid onto the haroom team as well at some point.
Your best bet is to simply 3 heal with 3 tanks, the dps requirements are a joke for this fight and the extra healer inside the throne room (arguably the hardest to heal) is much safer. When I healed this on my pala I went with unbreakable spirit due to the personal CD which helped, but yeah go with 2 heals in there and you will find it will be much easier.
He needs to watch his timers for when they'll all be lining up. He has AM, DP, Bubble, and potentially externals from tanks (Sac, Vig) to help him out.
You can also push the bosses at a specific time so the timers never line up. I believe the timing is push them to 60% when the Toxic Mist timer has 20s on it, but I could be wrong. We've talked about it, but never bothered executing it.
You should have combination of your own personals + warriors vigilance / demo banner / rallying cry to help you out with falling ashes, just have someone on the outside call out 5 sec before it falls so you have time to prepare
Divine protection is by far the better option. Hand of purity will only reduce falling ash damage by 10% (but it will help a lot with the DoT)
The holy pala should beacon himself since the non-tank with Haromm actually takes an astonishing amount of damage. He should then heal the tanks and let the beacon heals come through to himself. Don't forget the pally can also bubble a falling ash, you also have devo, banners, vigilance and whatever monks can help with.
Haromm's side is basically high throughput, an extra healer can make it easier.