i like the idea, priest leveling can get realy hard, although i would prefer a stat based increase to this spells just to add some option to the class (similar things could be used on other clases to make stats more usefull other than enough for equipment)
from 0-479 points into wis =0.08 of spell damage per point 0-33%increase
from 480-540 points into wis =0.09 of spell damage per point 43-48%increase
from 541-639 points into wis =0.11 of spell damage per point 59-70%increase
from 640-739 points into wis =0.13 of spell damage per point 83-96%increase
740 points into wis = 0.15 of spell damage per point 111% increase.