Those 2 things are the main thing that can wipe a raid, if youre getting it that low its just a matter of repetition. Make sure they are managing the spiny plumes, steel cyclone hits the entire raid for like 3k which throws healers way off. I know our other group who killed it healed through it but there is no need.
It's a surprisingly easy and smooth fight when you control that. It's a pain for your tanks because they'll be on the other sides of the map but that's what CDs are for. You should only get 2 add phases anyway at the end so they can pop CDs + sprint and grab the spiny's.