In VoD, if your not the main tank than the only time you should be taking any damage is during the waves.
While Mass Heal seems to be the spell of choice in the mass casting, consider the following:
1. Mass Heal is slow or more expensive to cast (Quicken)
2. Mass Heal does 400 to Over 1K
3. Most party members will be in the 300 to 600 range
4. Curse Wounds can be placed on a party member at any time during a wave
5. Mass Healing is most effective if the group sticks together
6. VoD is an endurance race and not a sprint - It can actually be completed on Hard with two healing types (Cleric/FvS/Bard) without need for Pots (I've done it several times). They will go through a few scrolls.
7. Use of Heal Scrolls and Mass, Mod Cure on a party that stays grouped can go a long way in stretching resources