Imho Hun, it's not just you. I don't know how you handle the mechs, but I feel your healers should be trying to help out with the mitigation. I main heals, and I can confidently say I have this fight down solid. In my experience, healers should be applying stone skin/noct shield/Aldo (preferably crit/eye for an eye to make their and the tank's lives easier. I've seen lots of dark knights get insta killed by the buster, so I always make them a priority to keep shielded when MTing. Just make sure you use proper CDs and hope healers can assist to keep you alive.

I would say take a break and come back to it with a clear/calm head. It'll be fine deary, just try to relax. You'll get it (: