I just got this spell and figured I'd note that the wiki quest information is a little off, unless the quest was changed after it being written. For whom it may concern, I just finished the quest and had 216 TM / 293 holy magic. I did have targeted mastery, and aligned TM through Everild. My skills still wouldn't add up to a blended 300 average so the requirement is just a lower blended skill, or maybe has to do with stats or total magic ranks. I doubt its the latter though because the person who wrote the wiki said he had high 300's holy magic so his other magics were probably higher than my 200-280 range.
On another note, liking the spell. It kills extremely fast, so maybe I need to find some fire resistant mobs in the near future to get more casts off for exp purposes. (hello temple atik'ets).