I have heard from multiple people a rumor that an Undaunted Helmet will not drop if a Laurel appears in the loot of the final boss.
I have no idea if there is any validity to it. That's why I am posting here. The first day IC patch hit, I ran 4 dungeons and got 3 hats. Since then, I have got 70 Laurels and a lot of shoulders and hardly any hats. Something has felt off about the drop rate. Or maybe this is just the case with certain bosses. For some reason I have more engine guardian helmets than Bogdan, Nerien'th, Valkyn, Mephala, and Bloodspawn combined.
Next time you run a daily, screenshot your loot and let's see if there is something to this.