So healing this on my SCH today (through DF) I noticed a few things.
- This is a very healer intensive fight in late phases
- eruptions would 9/10 target at least 1 healer (no healing or only instant cast for around 10-15 seconds)
- This fight actively discourages grouping for heals

As I've only healed this through DF I'm sure that preformed groups only suffer healing issues in the final phase where there is laser dodging and constant room-wide AoE. For me, the intense healing started around Ifrit phase, as people in DF tend to get hit by either Ifrit or plumes while trying to dodge the other. overall though, I believe if players are avoiding what they can and mostly just getting hit by more unavoidable attacks, the only real intense healing area is the final phase.