It goes both ways. If it's "owner needs", RNG can spite you and have everything you want drop from someone else's map where you're not allowed to have it. Your map could be a dud that doesn't even spawn a portal.
Our FC just goes everyone rolls need on what they want. It has caused some drama with newer members because poor ring but it serves its purpose well enough.
This is why when our fc does maps we have it that one person collects all the loot (normally me as I have most retainers) Sells everything and then equally shares out the gil after. If someone wants and item they buy it directly from me for current mb value. Everyone brings in 2 or 3 maps depending on how many came and everyone gets equal money back ultimate fairness.
Just don't do 'owner needs' parties. If everyone brings a map, then it really doesn't matter whose map is whose, it's all RNG and they're all free-for-all.
I see a lot of people mentioning FCs or friends instead for maps, but that isn't an option for everyone. I, for one, wouldn't have resorted to PF if I had any friends/a proper FC in this game.
Free for all makes more sense in the long run I feel. You end up with the same amount of loot on average and it avoids situations where people steal, or the party disbands before everyone has had a chance to run their map. RNG may be a thing, but even with "Map owner needs" you can be subject to bad rng where your map yields no rare items and others maps do.
Free for all is the only way to do it. Fair, not subject to someone getting good rng on portal spawns, everyone has equal chance on items.
You also REALLY don't need a party of 8 to do maps, I've been to the bottom and beaten it as 3-4 people, so usually I just grab a few friends and we talk with each other on items (usually I get the mats and make things for the others, give people minion if we have it, etc).
make sure you put into the chat logs that you all agree to a your map your loot policy. and have everyone say yes. if someone breaks those rules you can report them to support desk for breaking a written agreement. this can be enforced and it does work.
That's why I only ever run with "FFA" map parties.