Example low level Looting Areas:
Shadowfang Keep
Walk in with Character A and clear the very first room of mobs. Where the stair case is that leads to the first boss. Put Character B in the corner of that room, at the bottom of the staircase. You can now pull every mob in the dungeon to Walden, Character B will be in loot radius of everything.
Wailing Caverns
Clear a path to the point where you jump down the long pit into the water below Verdan the Everliving with Character A. Make sure you kill all the trash crocs so you don't have to worry about Character B. Place Character B at the bottom of the pit, making sure he's not underwater and can breath. You can now pull every mob in the dungeon to verdan the everliving with Character A, Character B will be in loot radius of everything. You will have to go to the west wing of the dungeon to be in the radius for cobrahn, but once you put Character B at the bottom of that area you can pull all the mobs to Cobrahn and Character B will be in looting Radius.
Ragefire/Deadmines/Gnomer
These are boss to boss areas. You'll have to pull all the mobs to the boss you need with Character A, then get on Character B and run to Character A while the mobs are attacking Character A. Make sure you pull every mob or Character B will die trying to reach Character A.