1 is enough..; mastering is waste of skill point and mana. When you learn high quality magics -sacred wave, moon fog, and judgement of god- you don't need to learn more then one. Well there are some combat healers who learn sacred wave and moon fog more then one, but it's really wasted of skill point and mana;;;
Well, some healers do that but it's waste to master moon fog, because when you are playing PVP you don't have much chance to use moon fog. They easily cancel it with other skills. Mastering is not good for PVE, too, because it wastes too much mana.