Say after you complete all the delves and public dungeons in a zone you unlock the ability to enter those public dungeons and delves as a harder instance. And this harder instance has a higher drop rate.
It'll benefit the game in a lot of ways!
- Min/maxers who farm for gear will opt to do their boss rotations in the hard mode, leaving the normal mode alone. Normal modes won't be a wasteland of already dead bosses.
- Players who just want an extra challenge to test themselves can return to an overland zone and try out the hard mode version of the public dungeons and delves.
- Players who like to group up for zone and guild dailies can choose the hard mode instances for a more entertaining daily.
- New achievements can be added giving a bit of new life to old content.
- Really incentivizes players to fully complete zones at some point.
- I'm sure there is more benefits! Like people no longer asking on the forums for harder overland content every day!