As a healer I really hate aggressive mobs, especially when there is a lot of them in one place, and especially in HW due to their tankyness.
If I need to do a quest battle somewhere, I really don't want to deal with some random mobs joining the fray, so I try to clear the immediate area, BUT even in Cleric my DMG output is rather low, and it happened more often than not that shit respawned before I was done with the clearing... "Fun" times...

So unless all quest battles are made as instances without trash around, I am completely against any sort of "harder overworld". You want challenge? Raid.