I'm pretty sure the 18 hours due to mine bots.

If you have multiple people in your group gathering maps, you can get 2 each of the peisteskin. Each person can carry two; use one to get the key item, then get the 2nd. You might even be able to collect 6-8 of them up yourself, then take a party of 3-4 out. I'm not sure if the sale slots on retainers count towards the unique counter.

Yeah the enemies are definitely too weak, I went out with a party of 8 and there was no challenge at all. It was about the difficulty level of a 45-50 FATE.