The only real way to fix the problems with Hunts in the short term is ,as many people have said, to limit the amount of marks a player can earn each week to (lets say) 500 a week, that's what 2.5 alexandrites, 1 Oil of time or 2/3rds of a Sands of Time. Or just allow Hunts to only provide Allied Seals so players when they finished with Enhancement items go back to dungeons for Tomestones

A better but longer term change would be (IMO) to link it to the Leve Allowances that players get each day to something like this. (please bar with me a sec)

Player gets 6 Allowances a day, they arrange can then try to arrange a party
they then go to the leaders Grand Company hunt board
From here they can chose which level of Mark Bill they want (B's costing 1, A's cost 2, S cost all 6 leves) that is chosen by the server at random and every member in the party pays the Leve cost
They then can go to the Zone and talk to the Hunter Scholar who gives them a Clue (i,e a general location clue)
Party can then follow the clue to the area and look for a Party Specific "Clue" (i.e. a footprint say) that they can activate for the fight
for rewards keep the Allied Seals the same just Lower (or as above remove) the amount of Myth/Sold you get

This way players who cannot (or will not) organize a party can get a fair reward per day (30 AS), while players willing to go that little bit further can earn more (say 60 if they do 2 A ranks, or 100 if they chose to do a S rank)