DreamWeaver has some good advice up there.

I suggest doing the following:

1) Have an agreement with your Scholar about who tops off each tank during the normal phases, ie. non-add phase. (In my group, I am default healing the PLD and the WHM is default healing the WAR). Only top off the other tank together pre-Secondary Head so they have some nice Stoneskins/Adloquiums on.

2) Don't panic the heals when you get used to the timings of the boss. Even if the tanks are kind of low pre-Nerve Gas, a fairy will top them off during this time in conjunction with Regen (unless your SCH is a scrub who has the fairy on Heel!). What you said about the Stoneskins during Nerve Gas is a good habit, but don't overkill it if the MP availability is simply not there.

3) The SCH needs to heal more during the add phase. The WHM should be topping people off with the AOE heals and throw in some complimentary Cures/Regens, but the SCH should try to keep Succor up and support the AOE-heals with fairy buffs when possible (if not using Selene, I swap to Eos at 60%). The SCH should be in charge of topping off both tanks, though you should try to utilize AOE-heals well enough that the Weapons Node -tank benefits of the heal splash as well. Your SCH can recover easily from the MP-strain of the add phase with Energy Draining on the nodes and re-Aetherflowing before Nerve Cloud. Depends on their timings and stack usage, but I try to help my WHM as much as possible during this phase (while DPSing a bit as well), so it's not uncommon for me to dip to 1.5k-2k MP as the Weapons Node and Gravity Node both die, whilst the WHM is at 3.5-4k~. Then I usually double Energy Drain on the Electric Node and have a new Aetherflow coming up pre-Nerve Cloud and I'm back to 3k+.

What DreamWeaver says about Resonance is true as well: the boss does a double Resonance on the pull and also after the first Nerve Gas, if the boss hasn't been pushed sub-90%. This hits hard. If you do push the boss sub-90% before the first Nerve Gas set has ended, the boss will cast Barofield and thereafter will only do singular Resonances after Nerve Gases. (And as DreamWeaver says, the singular Resonances also happen a bit after Secondary Head).