since all creatures have a skill already, the only purpose of light nymphs is the healing- and it is expensive for that.
replace them with sanctuaries- this will give you way more light quanta, so you can replace some pillars/pendulums with explosions/more sanctuaries.
miracle is possible as well.
FG decks aren't about being the strongest possible combination of elements. they are more about being thematic, and in this deck light nymph is more thematic than sanctuary or miracle (though that's not entirely obvious from the opening post i suppose.)
there are already far too many FGs that have miracle so i wanted to stay away from that. plus, its not very thematic here.
the light nymphs also provide muscle, and are a target for rage, without them the only rageable creature would be the archangels and the fire nymphs themselves. nymphs aren't really angelic i suppose, but there arent many options card wise and they seemed to fit well enough.