I guess that Rats, Amazons, Swamp Trolls, Frost Trolls, and Valkyries can be a good choice, along with severe other locations of different creatures that are concentrate on a place, specially on the Free Mainland Area, with small area respawns. Hellgate spawns can be worth it as well. Try to do what @Bust the Werriors said above, and throw fire bombs on many holes with these mentioned creatures. It will certainly help you out