+1
Dan33 is totally right in my opinion... there should be a SIGNIFICANT relationship between EFFORT and REWARD. This kind of SCALING of the difficoulty about hunting seems pretty fair to me, and if the quest, has to be accessible to ALL the players, it is not worth it anymore if the required mons are related to MS or specific location unlocked after completing a quest ( cerulean cave/pinkan island etc ).
For this reason i guees native Sinnoh region mons are accessible to everybody.
Last but not least,( Effort=reward ) but right now the quest is structured to hunt 7 days with random tier mons and no reward for 3 of 7 days.