The friendly NPC"s start running away at half HP though and it seems to only take 3-4 hits to get them to that halfway point. I had to constantly spam cure to try to keep them from running away and it seems like if 2 of the 3 npc's run the spirit targets me and just destroys me.
I'll advise you to completely ignore the other posters for a moment.
I'll be frank with you. You do not have to draw your weapon ,or even cast a spell to win that particular fight.
For the level 15 Gridanian quest, let your allies do all the fighting, and simply pay attention to the element the spirit becomes.
Once that element shifts, go to the Horned Kid and tell him what element to attune the resistance to.
Do this continually and your allies, even if they are defeated, will drop in and out of party and maintain constant pressure on the elemental, eventually defeating it.
The reason behind this is because the first quests designed in this game were designed with DOH and DOL jobs in mind. If you were say a Fisherman, and you were doing this storyline quest, you had no way to fight. The game was designed early so that even these jobs could beat these fights, making disciples of War and Magic completely unnecessary and often detrimental to them - this quest in particular standing as the example to that point.
In 2.0, the storyline will be centered around the disciples of war and magic. You'll have to have one leveled to progress through the main story. Disciples of Land and Hand will have their own side-quests just like the other classes will, and they will be more directed towards their stories. But you're encountering an old relic of a quest, so you have to play by it's strange rules.
Do not engage the elemental, do not support your allies. Let the Wood Wailers fight the spirit and you help the summoner kid do his thing properly. That's the guaranteed way to win. Edited, Aug 2nd 2012 12:07am by Hyrist