What's keeping people from working together now, or getting upset at one another for attacking a monster before everyone has arived?
The pure and simple fear that they themselves might not get enough hits in to get full contribution and thus the full rewards when the monster dies.
The hunts need but one simple insignificant change to be fixed, simply give everyone who got a hit in on the monster full credit and full rewards.
Getting rid of partial-credit essentially will mean that there's no reason for anyone to try and lock others out of attacking the monster, no point to resets other than maybe letting more people hit it, and i feel it should make everything a whole lot more casual and friendly. No one will get upset at other players if their own rewards are not hindered by having other people there.