You can farm by yourself or with others. Either way, you are just doing the same thing over and over again.
Henchmen get their own items from drops, the reason why sometimes monsters seem to drop nothing. It's because the items were assigned to the henchmen, and they are automatically picked up so you don't even notice they drop. Using henchmen assures you get less items, and in some cases that rare weapon you would've got is now pocketed by Alesia or Orion... and you don't even realize it.
Closed as there are plenty of topics about farming and drops.