Hey OP!
This link here shows you exactly what your problems are as far as executing the fight properly: https://www.warcraftlogs.com/reports...view=execution
As you can see, more than half of your raiders only used one potion. I know it sounds silly, but make sure all of your raiders knows what Pre-Potting is. I recommend Pre-Potting (Potting a second before entering combat) and using Heroism/Blood Lust right at the start of the fight. This will leave them with a second potion to use either in the execute phase or when ever they have a good ring/trinket/ability proc stack.
Moving past that, all together players stood in Blaze 47 times. Now, while this can be Cloaked, AMS, etc, it dealt 8.75 million damage to your raid in that one pull. The thing to keep in mind is that this always comes slightly during, and just after taking all of that unavoidable Quake damage. This can't be overlooked because while it may look like your healers can handle it fine in the start, it will over-tax them in the end.
On top of that, your raid took 5.80 million damage from the first set of pulverize, which simply requires all of your raiders to be standing spread apart from each other.
That adds up to 14.55 million completely unnecessary and avoidable damage taken so far. Add on 4.56 million for Arcane Volatility being splashed onto friendlies and you're up to just shy of 20.00 million 100% completely avoidable damage taken.
Have your players fix these things. Spend a couple attempts where your DPS literally doesn't even fight the boss but instead just dodges mechanics properly. It sounds silly, but wasting 20 minutes will save you a lot more time wasted (and headache) in the long-run.
Good luck with your kill!