kill between hotspots can stay on, it was just an idea but wouldnt have made a difference - have you done a fresh/clean install of ms .net 4 ?
what is your kill/pull distance set to also under settings > advanced
have you got loot mobs turned on ?
Unless Loot Mobs has been fixed in the latest release which I haven't read up on yet, Combat Looter plugin can be required to fix the targeting bug with Loot Mobs enabled.