Is there one Boss for each area, or only one Boss for the entire quest (if a quest is made up of multiple areas)?
If there is only one Boss for the entire quest, then learning the Boss's weakness is easier the more areas you have. In this situation, I suggest that in order to learn the Boss's weakness in a multi area quest, you have to collect a total number of clues equal to three times the number of areas in the quest [so, for example, if there are three areas you would need a total of 9 clues to discover the boss's weakness (3 x 3 =9)].