In pursuit of a learned smithing recipe, I needed to loot two axes and two machetes that said orc is known to carry. Upon arrival beyond the wall I tracked no lumberjack and no roaming pawns or centurions. Being in an old-world zone, I commenced killing all mobs there not in "camps", the snakes, the bears, the goblins, the bixies, the bats, everything. Shortly there appeared two lumberjacks, sequentially. Then an extended time passed with no pawns, no centurions , no lumberjacks. Eventually two friends joined me. The three of us continued killing random wandering mobs. It took us a long time -- hour plus -- to get enough lumberjacks to accumulate the required weapons. Conclusion: It is mandatory to kill from the entire wandering population to get enough lumberjacks and their weapons.
Another observation: The lumberjacks often get into battle with other mobs in there, often goblins but others also. When this happens, my inclination is to kill the lumberjack as quickly as possible. However, this is not fast enough. It is better to kill off the opponent of the lumberjack and follow the lumberjack until his health recovers; THEN kill him for the credit and loot.