Welcome to Eorzea!

Sadly I did that as a level 60 PLD (doing the GLA Hall of the Novice quests when they were added in a patch), but from what I remember, the idea is to lure enemies away from the npc using Shield Lob (gained with the level 15 GLA class quest), and once they are close, use Flash cycling in with Fast Blade and Savage Blade combo. I can't remember if you can use cross-class abilities in that though, otherwise I would suggest also cross-class Cure from CNJ and casting it on the npc to help keep them alive. But if you're using Shield Lob to grab the enemies quickly and then following up with Flash to keep the targets focused on you the ARC should be okay.

The key to succeeding in the Hall of the Novice is actually to follow the directions of what is being asked of you to do - in this case, build up hate by using the GLA's standard enmity tools: Shield Lob, Flash, and Fast Blade+Savage Blade. Provoke may work also with Flash immediately after, but I am not sure it works on protecting npcs - I think it only works in party situations sadly.

Either way, don't give up! You can do it!