Virus every DS you can.
Precast Cure 2 on DS.
Surecast Medica or Cure 3 is great on fireballs; the heal over time from Medica 2 will also help keep the conflag person from taking as much damage.
You can Regen somebody going into a conflag and it will heal more damage than the conflag deals.
If somebody (the tank) goes into a conflag while at low hp and needs a heal when coming out, try and time a Medica cast for right as the conflag dies. It isn't much, but you can't target them (and thus can't cast anything stronger) until they are out of it. Benediction is also an option, but if it's the tank you have to be FAST.
You have enough time to cast a heal between each individual divebomb.
Surecast is great for both fireballs (when they are targetting you) and the P3>P4 transition (when Twintania does the massive AoE). In both cases they let you charge a Medica/Cure 3 without fear of interruption.