If i remember rightly in IX this minigame gave a set time limit, alot of possible places to find mobs and more mobs than you could kill within the time limit given. You had to pick and choose what was worth spending time on and what wasnt, it was also important to save enough time to defeat the boss with. It was a fun minigame ^^

Im thinking it would be incredibly hard if not impossible to balance this so that all DOW/DOM/JOBS could do this as fast as the next one. I can also imagine that if Ranger is brought into xiv and gets widescan that job would have a big advantage in this sort of competition being able to scan the landscape and identify the monsters that will reward them the best points.
What comes to mind to try to make it fair would be that the mobs themselves would be tailored to each class/job. I would love to see SE implement something like this though provided possible balancing doesnt effect other PVE content.