About people rushing it in one day, that problem is easy to solve. All you have to make is like iBubble said an end boss in a dungeon you have to kill alone ot with a few people. Then you make different drops every end boss can have. Make some very rare items, which will rarely drop and make people do the dungeon over and over untill they get it. You can also add a few smaller drops and some guaranteed money drops like 100g.