I'd love to see where you got that, I'm sure it's a very interesting article.

Roman soldiers like any other soldier would have attempted to wound the enemy such that they were no longer threat, then immediately focused their attention on a more active opponent. As ancient battles with the Romans generally did not occur like they do in the movies (ie. a single charge and a slugging match until one side fell over) but rather could be an exchange of insults, missiles and repeated charges over many hours, the fates of wounded men would have been dependent on circumstances. Whereas wounded men falling in the thick of a real shoving match such as may have characterised hoplite warfare could easily have been trampled to death, the frequent separations between tired fighters in more extended battles between Romans and their enemies would have given opportunity for wounded men to remove themselves to the rear if they could move. They would not, however, have gotten much medical attention until the battle had ended, and obviously in Roman warfare, wounded men would be executed by a victorious enemy.

As for the 'capacity' or 'effectiveness' of Roman soldiers at killing people in battle, I have no doubt of that. While interesting texts like Grossman (On Killing, 1996) suggest that most humans find it psychologically extremely difficult to kill another person, I think the Romans were particularly proficient at killing. They put themselves at extreme risk in their very direct and committed method of waging war, and the Roman authorities cared very little for the lives or ransoms of defeated Roman soldiers. The Romans cared little for the lives of their own people, let alone those of the enemy. The gladius was a formidable killing weapon, as was the pilum, and an account exists (Livy?) of even experienced Macedonian hoplites recoiling in horror at the mass disembowelments and amputations inflicted by legionaries in combat. Romans were specifically taught to thrust whenever possible, as it was a more reliable killing blow (Vegetius). Much like the Germanic peoples the Romans spent so much time fighting, violence was very ingrained in their culture and killing an enemy in combat was considered something to be proud of. During the Republic, the greatest award a Roman (aristocratic) officer could receive was the spolia opimia, the armour of an enemy leader killed in hand to hand combat, taken back to Rome and dedicated to the gods. I don't doubt that many individuals, rendered anonymous and protected in formations of their heavily armoured fellows, would have fought more tentatively than the true killers that make up only a minority of soldiers (Sabin, Face of Battle, 11-12), but as a whole the Romans had no problem inflicting death and not even much problem risking it.

Mass killings of wounded enemies after battle would have been standard practice by the Romans, just as it was for their enemies (see Dio 56, the aftermath of the Varian Disaser). But a stabbing wound from a gladius would have been debilitating and generally fatal in short order. So Roman soldiers were on every level very effective at killing individuals in the heat of battle, but common sense applies: a soldier with an active enemy to his front would not waste attention on a fallen, wounded enemy. Someone behind him would deal with that if the opportunity arose.