In the DF/PUG/no-stated-rules PF, If I'm able to Need on an item, and I want the item...I'm Needing on it (or Greeding if no one can Need it). In my group's runs where we are running for specific items or have calls, I have no issues passing on things.

I have most Primal weapons; missing the Garuda SCH, Titan MNK and DRG, and Moogle BRD, MNK, PLD and BLM. I've been asked to pass (and have passed on) many Primal weapons for people, and I feel I have paid my dues now, so I'm not doing it anymore. If I can Need any of those...I'm going to.

Yes, recently I took the Ultima Choaker of Healing because I want it for my collection and Vanity (and it was the first thing from the fight I could actually Need on after many wins) despite having the Allagan Choaker of Healing; the SCH (I was WHM) was not happy, but he spent a good bit of the fight on the ground and honestly did not deserve it. If he had won the roll, then whatever, but he didn't.

Unless you come to an understanding with the other people that can Need your loot...you have to assume that you will be rolling against them. They have a right to roll on it by virtue of their class, and may have been going after that specific item for many runs. Just because you're undergeared doesn't mean you deserve it more (especially if you're not contributing as much as others, which happens more often than I like. So many people in Primal runs looking to be carried...)